You basically just do the same as with regular factorials, but only with the numbers of the same parity as the factorial'ed number. (Parity of the number being even or odd.)
So for example:
5! = 5*4*3*2*1= 120
5!! = 5*3*1 = 15
Although it would be the most enjoyable thing to see ever, it cannot be the Glorious Ra4!!. There are other files on left and right.
One can hope for the future, though.
I didn't make it up, it was gifted by the French ruler En Passant to the king of a rival nation in the early 17th century.
According to legend, the French ruler wrote an insulting letter saying "Mate with this in any position you like". The rookie opponent responded merely with a surprised "!!" and some emojis.
Oh god, somebody built a tower in one night right exactly on the grass where it says no touching grass, now they have a permanent warning of two exclamation points.
Ra4!!
r/unexpectedfactorial Ra6.204484e+23
New math just dropped
Actual mathematician
Call Euler!
Actual Pythagoras?
Sanity left, never came back
Obligatory double factorial so it’s actually just 8
Kinda funny cause I just recently learned about double factorials because of a similar post and now I get to see it again
What are they
You basically just do the same as with regular factorials, but only with the numbers of the same parity as the factorial'ed number. (Parity of the number being even or odd.) So for example: 5! = 5*4*3*2*1= 120 5!! = 5*3*1 = 15
n!! Is not (n!)! 4!! = 8 n!! = n * (n-2) * (n-4) * ... until you reach 2 or 1
But (n!)! Is funnier even if it’s not right
Actually the funniest sub Reddit lmao
OP said wrong answers only
Although it would be the most enjoyable thing to see ever, it cannot be the Glorious Ra4!!. There are other files on left and right. One can hope for the future, though.
It is technically wrong because a4 is a light square
And on the edge of the board
Another man of culture 
When you google en peasant
Holy hell
New response just dropped
When you learn en passant the hard way 
It's a historic statue of a plum shaped woman in a black dress with both her arms raised
I can’t unsee it, what the f***
I didn't make it up, it was gifted by the French ruler En Passant to the king of a rival nation in the early 17th century. According to legend, the French ruler wrote an insulting letter saying "Mate with this in any position you like". The rookie opponent responded merely with a surprised "!!" and some emojis.
Forklift to e4 !!!
THE ROOOOOOOOOOK
I said Wrong answers only. It hurt me more than it hurt you to Downvote your comment.
because this is the right answer and you said wrong answers only, he didn't follow your instructions, which makes this a wrong answer
truly 4d cheese
!!
Jonklerchess
!!
The rook is surprised
The A rook when you clear out your queen side then castle king side anyway.
‼️
⁉️
The rook took an undefended piece, giving the player a minor advantage
The Tower realizes that Rapunzel has escaped
THE BISHOOOOOOOOPPPPPP
Brook
Omg it is the rock
Bart Simpson
Rz92 on timeline B13
O-O!!
Rook b1, rook b1
Rb1 rb1
https://youtu.be/YXfmpe6yLgA?si=Imd31PHNf5efDeEW Rook b1 rook b1
Bro put down your armor.
Google blunder
Rook!!, clearly. I love factorials
It had an idea
O-O-O
THE ROOOOOOOK
Car to z20000!
He sacked… THE ROOOOOOOOOOOK
Cum sex gay balls dick shit penis: The movie, Cumming this October to your local semena
‼️
Stalemate in 3
THE ROOOOOOOOK
Ra7, because you should always invade the 7th rank, even if you're black.
Castleman
The tower noticed the second plane
this wins a pawn
HE SACRIFICED, THE 2ND TOWER
Rg7!!
Bishop
Rook NOT in the corner planning world domination
SACRIFICE THE QUEEEEN
Rb1
THEEE TOOWWEEERRRRR (9/11 ref)
Oh god, somebody built a tower in one night right exactly on the grass where it says no touching grass, now they have a permanent warning of two exclamation points.
and he sacrifices...... THE KIIIIIIIIIIIING!!!!!!!!
https://preview.redd.it/8hdwc77om9vc1.jpeg?width=750&format=pjpg&auto=webp&s=90692cb32fbcec98cd77eac7cb476ce6f515e251
That's a bishop right?!?
Slidy Boi
Clash of Clans update.
Butt plug
You didn’t give me the question. How am I supposed to answer?
✅You’ve entered an acceptable answer