yes, !! is also a math symbol
ฝัง
- เผยแพร่เมื่อ 5 ก.พ. 2025
- We introduce the double factorial !!, also called the alternate factorial. This cute little bit of mathematical notation gives us a way to achieve an effect similar to the standard factorial but while skipping every other number. The double exclamation point will respect the parity of its number, and proceed accordingly. We'll see examples of the factorial and double factorial, and then discuss perfect matchings in graph theory to see an example of where the double factorial is the solution to a problem. #maths #graphtheory #mathematics
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You have the word "math" twice in the thumbnail alone and still refuse to admit it's plural. 🤣
! = excellent move
!! = brilliant move
And he sacrifices THE FACTORIAL!!!
@@vectorboom1982 is that a !!! magnificent move???
#ChessRelated
AND HE SACRIFICES THE QUEEEEENNNN!! **he sac'd the queen dance**
what
0!=1 is true both in math and in programming.
A classic!
False is not equal to true
Because programming is math
@@Jacobconnor525 let me break it down for you:
if 0 != 1:
print("True")
else:
print("False")
output:
True
@@WrathofMathoh god what’s classic factorial equal to
At some point mathematicians are just going to be writing equations that look like perfectly functioning English.
LMAO
4nd 0n 7he 1ntern3t, 3nglish 15 1ooking m0r3 lik3 m47h3m471cs.
Don’t give the category theorists an idea…
@@dylanm.36921nf3$+@+ 0n by dm dokoru
the volume of a pizza with height a and radius z is pi•z•z•a
reminds of this reddit bot I used to see that would reply to any comment where they had an ! after a number and would reply by computing the factorial. LOL.
It's so in "aksselly" style of Reddit, like you say "it was over 100!" and some dumbass "mis"interprets it as 100 factorial, completely neglecting the semantical context of the aforementioned. those people are the worst (I'm a math nerd)
@@jaydentplays7485i wanted to comment the actual factorial but there's no way I'm writing that whole number without finding a way to copy it from somewhere
93,326,215,443,944,152,681,699,238,856,266,700,490,715,968,264,381,621,468,592,963,895,217,599,993,229,915,608,941,463,976,156,518,286,253,697,920,827,223,758,251,185,210,916,864,000,000,000,000,000,000,000,000
@@cloudyfromtpotrealhere you go
93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000
@@tenebrae711its just a dumb joke dont take it so seriously :DDD
! - that's great!
!! - that's brilliant!!
!!! - that's crazy!!!
@@AbdAlHakamJunaid
!!!! - I'm a psychopath
I see whatcha did there hhhehehehehehehahahhaha 🧌
AND HE SACRIFICES THE ROOK!!
e4 or e5?
Or in Spanish notation:
n! -> ¡n!
n!! -> ¡¡n!!
yes 😂
😂😂😂
n! -> ¡ñ!
n!! -> ¡¡ñ!!
@@sergiocm2911 That's only in specific cases.
so then (n!)! = ¡(¡n!)!
Literally found an infinite sum for arcsin that utilized the double factorial and got mad when desmos didn’t support it lol
it can be expressed using regular factorials. Something like
(2n)!/(4ⁿ(n!)²)•x^(2n+1)/(2n+1). then you sum it up from n=0 to infinity
@@lukandrate9866i did end up doing that but i was still annoyed anyways lol
I'd like to see them add that, but if they just did it with the regular notation with multiple exclamation marks, it could break some older projects. Instead, they could do it with a subscript on the exclamation mark: subscript 2 for double factorial, 3 for triple, and so on.
Note that Desmos does support product notation, using which the double factorial can be written.
I wonder what 5!! is, would you just be screaming “FIVE”
Anyways I wonder what 5!!! is, would you just be screaming 10 or something (because uh, I think 5!!! would be 5x2 and that’s 10 for all you who haven’t done 1st grade)
turns out, you'd be screaming fifteen
@@WrathofMathFIFTEEN
@@WrathofMathFIFTEEN
@@WrathofMathFIFTEEN
@@WrathofMathFIFTEEN
At first I thought; 5!! Would intuitively be: 5!*4!*3!*2!*1! How would you write this then?
This is called the superfactorial, denoted sf. Specifically, it's the one used by Neil Sloane. In your case, you'd have sf(5).
34560
@@isavenewspapers8890 how does one then write, sf(5)*sf(4)*sf(3)*sf(2)*sf(1)
\prod_{n=1}^{5} n!
same
simply the difference between something great and something brilliant
I knew I wasn’t the only one…
Holy heck.
Did they do a rook sacrifice
Subfactorials are so underrated. I love to use them, especially for those problems where you have to take digits and make an expression that equals a given number. There are actually an infinite family of subfactorials, which are longer chains of exclamation points, such as n!!!! for the 5th subfactorial of n, or n * (n-5) * (n-10) etc.
@@th1v5 Shouldn't that be 5 exclamation marks?
what the fuck!?!? actually 5th subfactorial is not a thing, 5th factorial is
@@isavenewspapers8890 yea woops
Had a math assignment where I could use (n+1)!!!
No hesitation, best way to solve the problem
@@dalemonshateu6948 the correct kind of solution
The volume of an n-ball with radius r is given by this formula:
V_n(r) = 2^n ((π/2)^⌊n/2⌋ / n!!) r^n,
or, if you prefer,
V_n(r) = 2^n ((τ/4)^⌊n/2⌋ / n!!) r^n.
This formula, which is quite beautiful to me, features the double factorial function. Due to this, the double factorial will always hold a special place in my heart.
What is an n-ball?
@@Speed001 To start, imagine a circle. This circle lives in an infinite flat 2D space, known as a plane. Note that we're not counting the inside region as a part of the circle. In math terms, that inside region is called a disk.
Anyway, the radius of this circle is the distance from the center of the circle to a point on the circle. This distance is the same in all directions. No matter which point on the circle you choose, it'll always be the same distance from the center. So we define the circle like this: the circle is the set of all points in the plane that are a certain distance, the radius, away from a certain point, the center.
With a sphere, it's a similar story. Every point on the sphere is the same distance from its center. Therefore, the sphere is defined as the set of all points in 3D space that are a given distance, the radius, away from a certain point, the center. The inside of a sphere is another shape, known as a ball.
Now, let's talk about dimension. For example, a plane is a 2-dimensional object. But how do we know? Well, we need 2 coordinates so that we can label every point in the plane. There are different types of coordinate systems. The most popular is (x, y) coordinates, known as Cartesian coordinates. You can use a different kind of coordinate system, like polar coordinates, but you will always need at least 2 coordinates in a given system to span the entire plane.
So, what is the dimension of a sphere? Let's look at a real-world example. Earth is a ball, and its surface is a sphere-well, approximately. We have a system for identifying points on Earth's surface: the geographical coordinate system (GCS). This system has two coordinates: latitude and longitude. Latitude tells you how far north or south you are, and longitude tells you how far east or west. Using two coordinates, you can label any point on the surface of Earth. For example, the Great Pyramid of Giza has a latitude of about 28° N and a longitude of about 31° E. So, a sphere is 2-dimensional.
What about a circle? Let's take the equator of Earth, for example. If a point is constrained to fall on the equator, then we just need its longitude to know its location. That's only one coordinate, so the circle is 1-dimensional.
A circle is called a 1-sphere, and a sphere is called a 2-sphere. This concept can be generalized to other dimensions as well. The n-dimensional version of a sphere is called an n-sphere.
Now, remember how a disk is the region of a plane enclosed by a circle? You need 2 coordinates to label a point on the disk, so the disk is 2-dimensional. Meanwhile, a ball, the region of 3D space enclosed by a sphere, is 3-dimensional. A disk is called a 2-ball, and a ball is called a 3-ball. This concept can be generalized to other dimensions as well. The n-dimensional version of a ball is called an n-ball.
@isavenewspapers8890 i see, thank you. You meant n-dimensional versions.
@@isavenewspapers8890Thank you for the explanation! Do other formulas exist for other forms too?
@ You mean, like, other generalizations of shapes to n-dimensional space? Well, I know of a simple one.
An n-cube is the n-dimensional version of a cube-think squares and cubes, including the inside regions. A square with side length s has an area of s^2, and a cube with side length s has a volume of s^3. In general, the volume of an n-cube with side length s is given by this formula:
V_n(s) = s^n
So yeah, that one's not complicated.
Edit: I meant the cube has a volume, not an area. Oops!
It indicates a brilliant sacrifice of parts of equations in order to solve them.
"Why are the numbers yelling?" -- high school philosophy teacher when my group presented something about math to the class
Great time to share my funny philosophy teacher story. Class in college called "Thinking for Yourself".
Took a test, got a problem wrong, argued with the professor that my answer was in fact correct.
He agreed, then said "But the text says otherwise, so your answer is wrong".
PROTOGEN!!
@@tcatking9761i'm starting to get sick of this exact thing happenening every time i see one
@@WrathofMath Seems like the text is right by definition but incorrect. This is why you do not trust what is "right". In reality, only functional logic and mathematics are right, which will eventually give people who've declared contrary statements as "right" an unpleasant wake-up call
bro summoned the chess players
Hehe
I'm here 😃
@@Drxcture
Hehe same!! ❤
@@plokenv Yay! :D
I'm here
Is there use cases for n!!! , n!!!! etc?
And Would a way to abbreviate the amount of ! you write be that you replace the dot with a number?
So that way you could have any number of !, even a pi amount of !.
Which I think would work like:
9! = 9 * (9-pi) * (9-2pi)
I think you can just use a general product sign for this, denoted as Π. Π(k=0, n/3) (n-3k) which would give you n(n-3)(n-6)...(n-n). I think I screwed the upper bound of this multiplication, but you get the point
Triple and quadruple factorials work in the way doubles do (which skip every 2nd number)
Triples skip every 3rd number, and quadruples skip every 4th number. This can go on infinitely.
Example: 10!!! = 10x7x4x1
2nd Example: 10!!!! = 10x6x2
Absurd Example: 10!!!!! = 10x5
a use case could be for some infinite series if you feel lazy in the notation, maybe in some taylor series
!! Brilliant Move
Triple and quadruple factorials work in the way doubles do (which skip every 2nd number)
Triples skip every 3rd number, and quadruples skip every 4th number. This can go on infinitely.
Example: 10!!! = 10x7x4x1
2nd Example: 10!!!! = 10x6x2
Absurd Example: 10!!!!! = 10x5
Then, there's primorials. Primorials are much more complex, with it being subtracted by every prime number.
Example: 10# = 10x7x5x3x2
2nd Example: 30# = 30x29x23x19x17x13x11x7x5x3x2
I'd assume a double primorial (I don't think this exists), would act the same way as a double factorial.
Example: 10# = 10x7x3
So do triple etc factorials have similar uses as the double factorial, just in slightly more complex problems? Or would such uses be vanishingly rare?
Your teaching is very articulate and wow
Thank you!
They added brilliant moves to math
“It’s over 9,000!!” Just got a new meaning 💀
better name it “it’s over 2601218943565795100204903227081043611191
5218750169457857275418378508356311569473
8224067857795813045708261992057589224725
9536641565162052015873791984587740832529
1052446903888118841237643411919510455053
4665861624327194019711390984553672727853
7099345629855586719369774070003700430783
7589974206767840169672078462806292290321
0716166986726054898844551425719398549944
8939594496064045132362140265986193073249
3697704776060676806701764916694030348199
6188145562519559256691883082551494294759
6537274845624628824234526597789737740896
4665539924359287862125159674832209760295
0569669992728467056374713753301924831358
7076125412683415860129447566011455420749
5899525635430682886346310849656506827715
5299625679084523570255218622235813001670
0834523443236821935793184701956510729781
8043541738905607274280485839959197290217
2661229129842051606757903623233769945396
4191475175567557695392233803056825308599
9774416757843528159134613403946049012695
4202883834710136373382448450666009334848
4440711931292537694657354337375724772230
1815340326471775319845373414786743270484
5798378661870325740593892421570969599463
0557521063203263493209220738320923356309
9232675044017017605720260108292880423356
0664308988871029738079757801305604957634
2838683057190662205291174822510536697756
6030295740433879834715185526028053338663
5713910104633641976909739743228599421983
7046979109956303389604675889865795711176
5666700391567481531159439800436253993997
3120306649060132531130471902889849185620
3766669164468791125249193754425845895000
3115616829743046411425380748972817233759
5538066171980140467793561479363526626568
3339509760000000000000000000000000000000
0000000000000000000000000000000000000000
0000000000000000000000000000000000000000
0000000000000000000000000000000000000000
000000000000000000000000090!” (factorial of (6!)!, it should be 6x4x2! and that is 720! and that is 2601218943565795100204903227081043611191
5218750169457857275418378508356311569473
8224067857795813045708261992057589224725
9536641565162052015873791984587740832529
1052446903888118841237643411919510455053
4665861624327194019711390984553672727853
7099345629855586719369774070003700430783
7589974206767840169672078462806292290321
0716166986726054898844551425719398549944
8939594496064045132362140265986193073249
3697704776060676806701764916694030348199
6188145562519559256691883082551494294759
6537274845624628824234526597789737740896
4665539924359287862125159674832209760295
0569669992728467056374713753301924831358
7076125412683415860129447566011455420749
5899525635430682886346310849656506827715
5299625679084523570255218622235813001670
0834523443236821935793184701956510729781
8043541738905607274280485839959197290217
2661229129842051606757903623233769945396
4191475175567557695392233803056825308599
9774416757843528159134613403946049012695
4202883834710136373382448450666009334848
4440711931292537694657354337375724772230
1815340326471775319845373414786743270484
5798378661870325740593892421570969599463
0557521063203263493209220738320923356309
9232675044017017605720260108292880423356
0664308988871029738079757801305604957634
(I removed a lot to not absolutely decimate your device)
I wish I had learned about the double factorial 6 months ago when I was learning about taylor and maclorian series... This would have been so damn helpful for simplifying things instead of writing it with only single factorials and exponentials
Haven't knew double factorial and other multifactorial until now. i made the same mistake before i knew. super helpful!
Thanks for watching! There are a lot of weird factorial operations, will definitely talk about more in the future
Not a mistake, but a possible interpretation of 3!! = (1x2x3)! =6!
@@MyOneFiftiethOfADollar yeah, that's how i interpret it before i knew it. even my android calculator do this. but just a week ago, i know multifactorial. never has something, fooled everyone. 💀💀💀
that's a brilliant move!
What a *brilliant* symbol.
Now we can do maths with EVEN MORE enthusiasm!!
"!!" Is the sum of a brilliant move
But the derivative of a brilliant is a blunder 💀
and he sacrificed, PEMDAS!
@@doughnutplayz and he sacrificed, Algebra!!
At This Point ? Might Be A Symbol Of Math
TL;DW: !! is a factorial, but skip the numbers that aren't the type of _n._ So 7!! = 7 x 5 x 3 x 1 (skip evens, only odds and vice versa for even numbers)
Next, the solution to the collatz conjecture will be “Wow^ie that(sUre/was) hard!!”
👁️👄👁️
I did 6!! on a calculator and it counted it as a number so awfully big, it’s considered infinity
It probably read (6 factorial) factorial then
@ yeah it did
probably read it as (6!)! and that would be 6x5x4x3x2x1=720
and that makes the (6!) into 720 and it becomes 720!, yeah, not even I could do that first one without a calculator and 720! IS SO LARGE IT TAKES UP MORE THAN HALF OF THIS REPLY: 2601218943565795100204903227081043611191
5218750169457857275418378508356311569473
8224067857795813045708261992057589224725
9536641565162052015873791984587740832529
1052446903888118841237643411919510455053
4665861624327194019711390984553672727853
7099345629855586719369774070003700430783
7589974206767840169672078462806292290321
0716166986726054898844551425719398549944
8939594496064045132362140265986193073249
3697704776060676806701764916694030348199
6188145562519559256691883082551494294759
6537274845624628824234526597789737740896
4665539924359287862125159674832209760295
0569669992728467056374713753301924831358
7076125412683415860129447566011455420749
5899525635430682886346310849656506827715
5299625679084523570255218622235813001670
0834523443236821935793184701956510729781
8043541738905607274280485839959197290217
2661229129842051606757903623233769945396
4191475175567557695392233803056825308599
9774416757843528159134613403946049012695
4202883834710136373382448450666009334848
4440711931292537694657354337375724772230
1815340326471775319845373414786743270484
5798378661870325740593892421570969599463
0557521063203263493209220738320923356309
9232675044017017605720260108292880423356
0664308988871029738079757801305604957634
2838683057190662205291174822510536697756
6030295740433879834715185526028053338663
5713910104633641976909739743228599421983
7046979109956303389604675889865795711176
5666700391567481531159439800436253993997
3120306649060132531130471902889849185620
3766669164468791125249193754425845895000
3115616829743046411425380748972817233759
5538066171980140467793561479363526626568
3339509760000000000000000000000000000000
0000000000000000000000000000000000000000
0000000000000000000000000000000000000000
0000000000000000000000000000000000000000
000000000000000000000000000
6! is already 720 and I don't wanna imagine how big 720! is
Math got brilliant moves now? what did I miss 😭😭😭
So 9!!! = 9×6×3 = 162 (only the numbers which have the same remainders when divided by 3)
the symbols of ! and !! are also used in chess. the ! means a great move and the !! means a BRILLIANT move. !! > !
So, 7! = 7!! x 6!!
Also 6! = 6!! x 5!!
etc.
Another fun one: 10! = 6! x 7!. Therefore, 10! = 7!! x (6!!)^2 x 5!!.
And it is called a brilliant move
someone should also opt for !!! triple factorial
!! is also the symbol in chess for “Brilliant” like this video’s spo-
this is brilliant
And he sacrifices... THE FACTORIAL!!
brilliant move !!
♙♙♙
🧙🏿♀️
??
@@prenstopper that’s a blunder
Brilliant!
Thanks for watching!
@@WrathofMathyou don’t get the joke do you?
@@Potato_neo I didn't when I replied, I do now after seeing a dozen more comments like this
Great move and Brilliant move.
Take it or leave it.
leave it
! = great
!! = AND HE SACRIFICED... DUH RUUUUUUUUUUUUUUUUUUUUUK!!!
!! is briliant move
5:04 tower of paradise
mf liked my comment as if bro knows😭
BRILLIANT MOVE
Great Move, Brilliant Move.
There are very, very few commercially available calculators (if any) that support double factorials. Even high end calculators like the TI nspire CX II can't do them.
They don't come up very often, no, but they'd be very easy to implement, so... Why not?
Didn't know you can sacrifice odd or even numbers with this brilliant move. Jokes aside, this really was insightful to watch. Thank you for making this!
Can tou go over this again more because MAN I loved Golden Eye and I feel like you only scratched the surface here!
Me as a speedcuber that hears the word “parity” (aka a state of a rubiks cube that cant be solved with only the outer layer turns or has to be solved with a really long algorithm) (aka a pain in the ass)
same
same
Are there prize paying speed cubing tournaments?
@@MyOneFiftiethOfADollar Yes, there are!
@@geopediashorts big bucks?
3:09 what is this gorgeous music????
brilliant move
4:37 unintended coding pun? (you could probably "bang" out a couple others
From all i know the !! Means that a move was briliant and ! Means that the move was exelent
You can also write n! as n!! times (n-1)!!
Very clear presentation!
Thank you!
brilliant move!
Bro 😂 I just said to my mom before we went on a 1-2 hrs road trip "I am a dyslexic purple hotdog" and the first part of the video played the "Yes it's true" 😂😂😂😂😂😂😂😂😂
So 8!! * 7!! = 8! 😮 Actually n!! * (n-1)!! = n! provided n > 0
It's not quite as pretty but:
Define 𝑛 ∈ 2ℕ = {2,4,6...} or
𝑛 ∈ 2ℕ - 1 = {1,3,5...} for odd numbers.
With that you can do a lot more customization like ℕ³ = {1,8,27,64...}, with the 4th cubic factorial number being 13824.
Edit: Also ∏(𝑛³) from 1 to 𝑘 would be the same effect as the above without having to imply that the factorial applies to a certain set.
The... What- 💀
Mathematicians are like the British museum
! (Bang) and !! (Bang bang) are both useful in the C language
Funny, I actually guessed the right answer. I was a bit loo lazy to solve it completely, but n!/n!! seemed like it would make sense, but then I realized that's actually the same as n(-1)!!, because all the other numbers cancel out!
Maths made a brilliant move…
he got us in the first half, not gonna lie
I never knew Great and Brilliant moves were in math
Now we need a triple factorial
Yeah, the !! Means brilliant move
Brilliant!!
The factorial is great, but the double factorial is brilliant!!
Brilliant move!!
What if we want to know the number of triangular matchings in a complete graph, k3 only one, and k4 would have 4 (abc,abd,acd,bcd)???
Nobody should use that symbol as it's confusing ... for me, n!! = (n!)! and nothing else.
I don't see anyone else complaining about it being confusing. Others can use whatever symbol works for them, and you can invent your own notation if you want. Actually, there already is one, which consists of putting a subscript 2 on an exclamation mark; maybe you'll like that one.
7:25 are you a robot? It sounded like your voice was on a flanger for a sec there when you have a pair of headphones
Explanation: So 1!=1x1=1 And 3!=1x2x3=6 While 3!!=The factorial of 3! or 6!. And there is 3!!! Or 6!!. Hope this enjoyed!
Anything is a math symbol if you believe hard enough
i believe
I think I heard this called a double exclam post operator in grad school study groups once?!(interrobang)
Like you said, a natural interpretation is n!! = (n!)!
Your excellent graph theory exposition clearly justified the parity based definition n!! = n(n-2)(n-4)....1
What happened to the coffee pot dude?!?!?
didnt watch the video, but in mathematics, !! is used to indicate that an equation is very cool and brilliant
brilliant symbol
so is n!!! the factorial of all the numbers from n-3 down to 1?
Excellent video!
Thank you very much!
It indicates a brilliant sacrifice of your computers ram.
14:23 who is hearing Dire Dire Docks?
Super helpful, thank you :)
It is my pleasure!
9!! is [00],[945], 10!! is 15,360, 11!! is 10,395, 12!! Equates 46,080, and 13!! |is equal to| 132,935.
Its a very great math and chess sembol to be
So 0! = (e^ipi)^2 = 1^2 = sqrt(1)
04:30 on even numbered double factorial...
"You could include 1 if you want to..."
Can you?
You said parity, "even or odd numbers only",was the definition of double factorial.
1 is an odd number.
Wouldn't every even "!!" end in zero?
8!!=(8*6*4*2*0) ?
no, you only continue the multiplication down through positive integers.
I only said you could include 1 as a passing remark, where people might wonder what the stopping point of the multiplication should be. Of course, typically it's 1; but I should have addressed 0 rather than flippantly throwing out the 1 remark.
what about !x!
subfactorial of x factorial
it looks horrifying
What if that pattern continued? Like, say, !!! for all numbers of the same residue class mod 3? (As in, 8!!! = 8•5•2)
I now realize that I'm not the first one to think of this ^.^"
n!! is so cool how about the swinging factorial tho
Jeeeez, I was looking up weird factorials the other week and I never heard of that one! Will have to investigate; there are so many!
Look at my comments if you can.
Its amazing factorial.
I formatted before one year ago and its so useful.
@@WrathofMathcool
3!!=720
Brilliant move
(16*1000)+8!!=2^14
brilliant
Double the factories, less than half the production? We're going to starve!
I promise, this is my hypothesis prior to watching the video but seeing the title: The double exclamation point (!!) is going to be something like double factorial or something.
she edge my node till i graph theory
...bruv
@WrathofMath 😈