# Questions tagged [combinatorics]

For challenges involving combinatorics.

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### Centerless Polygons

A centered polygonal number is a positive integer given by the number of vertices when a point is surrounded by (increasingly larger) polygons with the same number of sides, as shown below. For ...
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### Dobble Double Challenge [closed]

I have a problem, which I haven't found a solution for. Solutions to the first part are well documented, but I have yet to find anyone who has solved the second part. I call this the "Dobble"...
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### Rectangles in rectangles

This code-golf challenge will give you two positive integers n and k as inputs and have you count the number of rectangles with ...
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### Sequences of distinct positive integers

The goal of this challenge is to take a positive integer n and output (in lexicographic order) all sequences $S = [a_1, a_2, ..., a_t]$ of distinct positive ...
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### Extend the most recent "nice" OEIS sequence: stepping stone puzzle on a grid

Today Neil Sloane of the OEIS sent out an email asking for a confirmation of the current terms, and computation of some larger terms of the latest OEIS sequence A337663 with the keyword "nice&...
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### Maximal saturated domino covering of a rectangle

Inspired by this OEIS entry. Background A saturated domino covering is a placement of dominoes over an area such that the dominoes are completely inside the area, the dominoes entirely cover the ...
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### Tiling a staircase with staircases

Background A staircase polyomino is a polyomino made of unit squares whose shape resembles a staircase. More formally, a staircase polyomino of size $n$ is defined as follows: A staircase polyomino ...
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### Cut a triangle into equal-sized parts!

Similar in spirit to Number of distinct tilings of an n X n square with free n-polyominoes and Partition a square grid into parts of equal area, this challenge will have you count ways of partitioning ...
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