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PROJECT EULER · #0805

Shifted Multiples

Statement only · UnsolvedOriginal problem ↗

For a positive integer n, let s(n) be the integer obtained by shifting the leftmost digit of the decimal representation of n to the rightmost position.
For example, s(142857)=428571 and s(10)=1.

For a positive rational number r, we define N(r) as the smallest positive integer n such that s(n)=rn.
If no such integer exists, then N(r) is defined as zero.
For example, N(3)=142857, N(110)=10 and N(2)=0.

Let T(M) be the sum of N(u3/v3) where (u,v) ranges over all ordered pairs of coprime positive integers not exceeding M.
For example, T(3)262429173(mod1000000007).

Find T(200). Give your answer modulo 1000000007.

Write-up coming later

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