12 questions linked to/from One OEIS after another
8k views

### 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/...
• 73.8k
3k views

### 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 ...
• 196k
6k views

### 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 ...
• 21k
6k views

### Levi-Civita symbol

The three-dimensional Levi-Civita symbol is a function f taking triples of numbers (i,j,k) each in ...
• 144k
2k views

### 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 ...
4k views

### 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 ...
• 2,329
1k views

### 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 ...
• 3,831
811 views

### 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 ...
• 20.6k
846 views

### 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 ...
• 46.5k
2k views

### 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, ...
• 12.2k
884 views

### 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 ...
• 8,659