{"app":{"locale":"en-GB"},"problem":{"content":"

Let $\\varphi(n)$ be Euler's totient function.

Let $f(n)=(\\sum_{i=1}^{n}\\varphi(n^i)) \\text{ mod } (n+1)$.

Let $g(n)=\\sum_{i=1}^{n} f(i)$.

$g(100)=2007$.

Find $g(5 \\times 10^8)$.

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