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Problem #260

Totient sum

Let L = \sum_{n=1}^{\infty} \frac{\varphi(n)}{2020^n - 1} Here \varphi(n) is the totient function. It can be shown that L can be represented as \frac{P}{Q}, where P and Q are coprime integers, and Q \not\equiv 0\pmod{1000000007}. Find the value of P\cdot Q^{-1} modulo 1000000007.

Contributed by Sawarnik Kaushal

Solved by 46 users

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