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PROJECT EULER · #0639

Summing a Multiplicative Function

Statement only · UnsolvedOriginal problem ↗

A multiplicative function f(x) is a function over positive integers satisfying f(1)=1 and f(ab)=f(a)f(b) for any two coprime positive integers a and b.

For integer k let fk(n) be a multiplicative function additionally satisfying fk(pe)=pk for any prime p and any integer e>0.
For example, f1(2)=2, f1(4)=2, f1(18)=6 and f2(18)=36.

Let Sk(n)=i=1nfk(i). For example, S1(10)=41, S1(100)=3512, S2(100)=208090, S1(10000)=35252550 and k=13Sk(108)338787512(mod1000000007).

Find k=150Sk(1012)mod1000000007.

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