$17\mid19^{8n}-1\;\;\forall n\in\mathbb{N}$?

$17\mid19^{8n}-1\;\;\forall n\in\mathbb{N}$?

Show that $17\mid19^{8n}-1\;\;\forall n\in\mathbb{N}$. I thought about
using arithmetic of the remains, proving that $1\equiv19^{8n}\pmod{17}$
And I could not do it: (