## Calculus 8th Edition

$\lim\limits_{n \to \infty}\sqrt[n] a_{n}=\lim\limits_{n \to \infty}\sqrt[n] {(\frac{n!}{n^{4}})^{n}}$ $=\lim\limits_{n \to \infty}\frac{n!}{n^{4}}$ $=\infty$ \gt 1\$ The series is divergent by root test.