Linked Questions

57 votes
154 answers

The vanilla factorial challenge

Task Given a non-negative integer \$n\$, evaluate the factorial \$n!\$. The factorial is defined as follows: $$ n!=\begin{cases}1 & n=0\\n\times(n-1)!&n>0\end{cases} $$ Rules All default I/...
Bubbler's user avatar
  • 76.9k
29 votes
31 answers

Deranged !Combinatorics: Compute the Subfactorial

The subfactorial or rencontres numbers (A000166) are a sequence of numbers similar to the factorial numbers which show up in the combinatorics of permutations. In particular the nth subfactorial !n ...
Martin Ender's user avatar
14 votes
29 answers

RLE Brainfuck dialect

RLE Brainfuck (related to BF-RLE) The hypothetical RLE (Run-Length Encoding) dialect of Brainfuck accepts the symbols for the 8 commands and also accepts digits. The digits are used to represent the ...
Galen Ivanov's user avatar
33 votes
21 answers

Levi-Civita symbol

The three-dimensional Levi-Civita symbol is a function f taking triples of numbers (i,j,k) each in ...
xnor's user avatar
  • 145k
19 votes
23 answers

How many partitions do I have?

The partition number of a positive integer is defined as the number of ways it can be expressed as a sum of positive integers. In other words, the number of integer partitions it has. For example, the ...
user avatar
25 votes
11 answers

Generate a Kolakoski sequence [duplicate]

Definition1 A Kolakoski sequence is a self-describing infinite sequence {kn} of alternating blocks of 1's and 2's, given by the following rules: k0 = 1 kn = the length of the (n+1)'th ...
ardnew's user avatar
  • 2,329
12 votes
21 answers

An OEIS polyglot

This is an answer-chaining challenge relating to the OEIS. Oh, the justification for this is because a company needs one program to print out their OEIS sequences real bad and they have every ...
AndrewTheCodegolfer's user avatar
11 votes
12 answers

Travel Back in Quine

The challenge here is simple, and not at all about byte-count. Your job is to output the first 50 characters of the previous quine's source code, concatenated with the first 50 characters of yours ...
Magic Octopus Urn's user avatar
16 votes
4 answers

Number of \$n\$-carbon alkanes

Given a positive number \$n\$, find the number of alkanes with \$n\$ carbon atoms, ignoring stereoisomers; or equivalently, the number of unlabeled trees with \$n\$ nodes, such that every node has ...
alephalpha's user avatar
  • 48.5k
11 votes
6 answers

Calculate the Kronecker symbol

Relevant links here and here, but here is the short version: You have an input of two integers \$a\$ and \$b\$ between negative infinity and infinity (though if necessary, I can restrict the range, ...
Sherlock9's user avatar
  • 12.3k
14 votes
2 answers

Counting generalized polyominoes

This challenge will have you count pseudo-polyforms on the snub square tiling. I think that this sequence does not yet exist on the OEIS, so this challenge exists to compute as many terms as possible ...
Peter Kagey's user avatar
  • 8,689
-2 votes
4 answers

Find the hardest OEIS sequence to golf!

Notice: This question originally had people write comments with a shorter program, rather than new answers. This has been changed so that people with shorter programs can get reputation too. Hopefully ...
pommicket's user avatar
  • 3,157