← Complete problem index

PROJECT EULER · #0560

Coprime Nim

Statement only · UnsolvedOriginal problem ↗

Coprime Nim is just like ordinary normal play Nim, but the players may only remove a number of stones from a pile that is coprime with the current size of the pile. Two players remove stones in turn. The player who removes the last stone wins.

Let L(n,k) be the number of losing starting positions for the first player, assuming perfect play, when the game is played with k piles, each having between 1 and n1 stones inclusively.

For example, L(5,2)=6 since the losing initial positions are (1,1), (2,2), (2,4), (3,3), (4,2) and (4,4).
You are also given L(10,5)=9964, L(10,10)=472400303, L(103,103)mod1000000007=954021836.

Find L(107,107)mod1000000007.

Write-up coming later

The complete problem is available here. An approach, code, and answer will be added later.