((1/2)/p^2)*(T(p)-1) where p runs through the prime >= 5 and T(k) is the k-th central trinomial number (A002426).

A087178

((1/2)/p^2)*(T(p)-1) where p runs through the prime >= 5 and T(k) is the k-th central trinomial number (A002426).

Terms

    a(0) =1a(1) =4a(2) =106a(3) =630a(4) =26185a(5) =178666a(6) =8991709a(7) =3678166249a(8) =28031525940

External references