53 votes

Absolute Sums of Sidi Polynomial Coefficients

Python 2, 43 bytes f=lambda n,k=1:k/n or n*f(n,k+1)+k*f(n-1,k) Try it online! A different approach Ever since I posted this challenge, I tried to come up with a ...
Dennis's user avatar
  • 210k
31 votes

Anaglot Polygrams

34 Languages, 19 bytes, Score: 38,832,018,459,912,437,760,000 Here is a quick answer I threw together to show that it is possible to get an answer scoring better than 1. ...
Wheat Wizard's user avatar
  • 96.5k
29 votes

Every word from babab to zyzyz

Mathematica, 72 65 61 bytes Print@@@Tuples@{a=##/(b=#5#9#15#21#25#)&@@Alphabet[],b,a,b,a} For testing, I recommend replacing ...
Martin Ender's user avatar
28 votes

Catalan Numbers

C, 78 52 39 34 33 bytes Even more C magic (thanks xsot): c(n){return!n?:(4+6./~n)*c(n-1);} ?: is a GNU extension. This time by ...
Stefano Sanfilippo's user avatar
26 votes

Concentric rings on a snub square tiling

Ruby, 26 bytes ->n{~-n*12-496/4**n%4+1/n} Try it online! Revised version adding 1/n and subtracting ...
Level River St's user avatar
25 votes

Bernoulli Numbers

Mathematica, 40 28 23 22 bytes Using the famous formula n*ζ(1−n)=−Bn, where ζ is the Riemann Zeta function. If[#>0,-Zeta[1-#]#,1]& The same length: <...
alephalpha's user avatar
  • 46.5k
25 votes

Catalan Numbers

Jelly, 4 bytes Ḥc÷‘ Try it online! How it works ...
Dennis's user avatar
  • 210k
25 votes

The square root of the square root of the square root of the…

APL (Dyalog Unicode), 39 bytes +/⊢{∨/⍺⍵<⍵0:0⋄⍺=0:1⋄+/∊∇¨/⍺(⍵*2)-⊂⍳⍺}¨⍳ Try it online! A tacit function containing an inner dfn to use recursion. Does not use ...
Bubbler's user avatar
  • 73.8k
24 votes

Sticky polyhexes

Haskell, 320…236 230 bytes ...
Delfad0r's user avatar
  • 6,236
24 votes

Counting universal n-ary logic gates

Python 3.8 (pre-release), 287 282 242 bytes -5 bytes thanks to @Dialfrost ...
AnttiP's user avatar
  • 7,828
23 votes

Compute the multinomial coefficient

Jelly, 7 6 bytes ;_/!:/ Look ma, no Unicode! This program takes a single list as input, with n at its first index. Try it online! or verify all test cases at ...
Dennis's user avatar
  • 210k
23 votes

Brute-force the switchboard

Haskell, 25 24 23 17 bytes mapM$min"^v".pure Try it online! -1 byte thanks to @H.PWiz -1 byte thanks to @nimi Returns a list of strings. The TIO has 2 extra ...
cole's user avatar
  • 3,976
21 votes

Don't repeat yourself in Rock-Paper-Scissors

Ruby, 39 bytes ->n{(?P*n..?S*n).grep_v /[^RPS]|(.+)\1/} This hilariously inefficient function generates all strings of length N that lie alphabetically ...
histocrat's user avatar
  • 22.1k
20 votes
Accepted

The Combinatorics of Transistor

CJam (56 bytes) q~4@:Nm*:$_&{:+1$\-N),&},f{1$1$:+-\0-:(_e`0f=+++:m!:/}:+ Online demo This is an optimised version of the reference implementation I ...
Peter Taylor's user avatar
  • 43.1k
20 votes

Count sums of two squares

Python (59 57 56 bytes) lambda n:0**n+sum((-(n%(x-~x)<1))**x*4for x in range(n)) Online demo As with my CJam answer, this uses Möbius inversion and runs in ...
Peter Taylor's user avatar
  • 43.1k
20 votes

Deranged !Combinatorics: Compute the Subfactorial

Funciton, 336 bytes Byte count assumes UTF-16 encoding with BOM. ...
Martin Ender's user avatar
20 votes

Partitioning the grid into triangles

Haskell, 60 55 54 52 bytes After a drawing and programming a lot of examples, it occured to me that this is the same as the problem of the rooks: On a \$(n+1) \times (n+1)\$ chessboard, how many ...
flawr's user avatar
  • 43.7k
19 votes

Stuffing primes in a box

Smalltalk, 1098 primes First off, nice hard question - as evidenced by the lack of non-trivial responses thus far. I had a solution cooking at work, but had to wait for the long weekend to have time ...
Amos M. Carpenter's user avatar
18 votes

A penny saved is a penny

Haskell, 37 34 bytes s#l@(c:d)|s>=c=(s-c)#l+s#d s#_=0^s Usage example: 26 # [1,5,10,25] -> ...
nimi's user avatar
  • 35.8k
18 votes

Converge to a number

Jelly, 9 bytes DLḶU⁵*xDÄ Try it online! ...
Lynn's user avatar
  • 68.1k
18 votes

Enumerate all pure sets

Python, 43 bytes f=lambda x:[f(i)for i in range(x)if x>>i&1] Attempt This Online! Outputs the \$ n \$th set, starting at \$ 0 \$. One way of creating a sequence of all pure sets is to encode ...
pxeger's user avatar
  • 23.3k
17 votes

Code-Golf: Permutations

Python, 52 Input is a set. Output is a list of lists. f=lambda a:[p+[x]for x in a for p in f(a-{x})]or[[]] This is shorter than the answer that does all the work ...
feersum's user avatar
  • 31.3k
17 votes
Accepted

Generate all combinations of given list of elements, sorted

Jelly, 1 byte TryItOnline Cartesian power built-in atom, as a dyadic link with left argument the items and right argument the count, or as a full program with ...
Jonathan Allan's user avatar
16 votes

Count sums of two squares

Python 2, 44 bytes f=lambda n,x=1:+(x>n)or(n%x<1)-f(n,x+2)/4<<2 This is almost the same as xsot's solution (which is based on Peter Taylor's solution)...
Mitch Schwartz's user avatar
16 votes

Super permutations

Scratch 3.0, 65 blocks / 637 632 bytes Look at y'all, having fun with your fancy shmancy permutation functions/map tools. Well, not I! No, not I! When using Scratch, one has to do things themselves! ...
lyxal's user avatar
  • 32.3k
16 votes

Never trust a mastermind

JavaScript (ES6),  116 112  107 bytes Expects an array of entries in the following format: [[a,b,c,d], "XY"], where a ...
Arnauld's user avatar
  • 188k
16 votes
Accepted

Cut a triangle into equal-sized parts!

JavaScript (ES7),  367 362 359  357 bytes Saved 1 byte thanks to @Shaggy Expects (n)(m). ...
Arnauld's user avatar
  • 188k
16 votes

Just Enough Ones

J, 41 bytes 1#.*:=1#.2>[:>@~.@,[:+&,&.>/~i.@!<@A.=@i. Try it online! A different take on brute force, which handles up to n=6 on TIO. Since the ...
Jonah's user avatar
  • 33k
15 votes

Count sums of two squares

Mathematica, 13 bytes If built-ins are allowed, this is how to do it in Mathematica. 2~SquaresR~#& For 0 < = n <= 100 ...
DavidC's user avatar
  • 25.3k

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