## Calculus (3rd Edition)

The series $\sum_{n=1}^{\infty} (2/n)^n$ converges.
To apply the root test, we have $$L=\lim _{n \rightarrow \infty} \sqrt[n]{a_{n}}=\lim _{n \rightarrow \infty} \sqrt[n]{(2/n)^n}=\lim _{n \rightarrow \infty} \frac{2}{n}=0\lt 1$$ Hence, the series $\sum_{n=1}^{\infty} (2/n)^n$ coverges.