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PROJECT EULER · #0929

Odd-Run Compositions

Statement only · UnsolvedOriginal problem ↗

A composition of n is a sequence of positive integers which sum to n. Such a sequence can be split into runs, where a run is a maximal contiguous subsequence of equal terms.

For example, 2,2,1,1,1,3,2,2 is a composition of 14 consisting of four runs:

2,21,1,132,2

Let F(n) be the number of compositions of n where every run has odd length.

For example, F(5)=10:

54,13,22,32,1,22,1,1,11,41,3,11,1,1,21,1,1,1,1

Find F(105). Give your answer modulo 1111124111.

Write-up coming later

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