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Problem #360

Phir Se Wahi Phi

Let C(n) be \sum (\phi(a) \times b) taken over ordered pairs (a, b) of positive integers for which a \times b divides n.

Let F(k) = \sum_{i=1}^{k} \frac{C(i)}{i}.

Let x = \sum_{k=1}^{\infty} \frac{F(k)}{k \times 2^k}.

Output \lfloor x \times 10^5 \rfloor.

Contributed by SHUBHAM KUMAR VERMA

Solved by 3 users

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