if postive integer $n$ such $n|2^n-2$,where $n>1$, we called $n$ is Poulet number,see:https://en.wikipedia.org/wiki/Super-Poulet_number I found if $n$ is Poulet number,then $\dfrac{2^n-2}{n}$ always is composite number Is this a known result? if $n$ is odd number,so $\frac{2^n-2}{n}$ is even number,and $\frac{2^n-2}{n}>2$,so $\frac{2^n-2}{n}$ is composite number. But for $n$ is even number.I can't prove it