a(n) = ( A000111(p) -(-1)^((p-1)/2) )/p, where p = prime(n).

A180418

a(n) = ( A000111(p) -(-1)^((p-1)/2) )/p, where p = prime(n).

Terms

    a(0) =1a(1) =3a(2) =39a(3) =32163a(4) =1720635a(5) =12345020175

External references