a(n) = (2^(2*p - 1)) - 1, where p is A000043(n).

A139307

a(n) = (2^(2*p - 1)) - 1, where p is A000043(n).

Terms

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

External references