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Test the given series for convergence or divergence

Determine if the following series converges or diverges and justify your decision.

    \[ \sum_{n=1}^{\infty} \left( n^{\frac{1}{n}} - 1 \right)^n. \]


The series converges by the root test since

    \begin{align*}  \lim_{n \to \infty} a_n^{\frac{1}{n}} &= \lim_{n \to \infty} \left( \left( n^{\frac{1}{n}} - 1\right)^n \right)^{\frac{1}{n}} \\[9pt]  &= \lim_{n \to \infty} \left(n^{\frac{1}{n}} - 1\right) \\[9pt]  &= 0 < 1. \end{align*}

Hence, the series converges.

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