2^(2p - 1) - 1, where p is prime.

A139287

2^(2p - 1) - 1, where p is prime.

Terms

    a(0) =7a(1) =31a(2) =511a(3) =8191a(4) =2097151a(5) =33554431a(6) =8589934591a(7) =137438953471

External references