# One of three of a kind - Part (1)

**Calculus**Level 5

\[ \large \sum_{k=1}^\infty \frac{\phi(k)}k \ln(1 - x^k) \]

Let \( \phi(k) \) denotes Euler's Totient Function.

For \(0<x<1\), find the closed form for the series above.

\[ \large \sum_{k=1}^\infty \frac{\phi(k)}k \ln(1 - x^k) \]

Let \( \phi(k) \) denotes Euler's Totient Function.

For \(0<x<1\), find the closed form for the series above.

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