a(n) = ((-4)^((p-1)/4) - 1)/p, where p is the n-th prime congruent to 1 mod 4.

A318898

a(n) = ((-4)^((p-1)/4) - 1)/p, where p is the n-th prime congruent to 1 mod 4.

Terms

    a(0) =-1a(1) =-5a(2) =15a(3) =-565a(4) =-7085a(5) =25575a(6) =-1266205a(7) =-17602325a(8) =941362695a(9) =197665011735

External references