a(n) = (2^p - p^2 - 1)/6 where p = prime(n).

A166743

a(n) = (2^p - p^2 - 1)/6 where p = prime(n).

Terms

    a(0) =1a(1) =13a(2) =321a(3) =1337a(4) =21797a(5) =87321a(6) =1398013a(7) =89478345a(8) =357913781a(9) =22906492017a(10) =366503875645

External references