Mersenne numbers
From specialfunctionswiki
The Meresenne numbers $M \colon \{0,1,2,\ldots\} \rightarrow \mathbb{Z}$ are of the form $$M(n)=2^n-1.$$
The Meresenne numbers $M \colon \{0,1,2,\ldots\} \rightarrow \mathbb{Z}$ are of the form $$M(n)=2^n-1.$$