a(1) = 1, a(2) = (1+2)*(2+3), a(3) = (1+2+3)*(2+3+4)*(3+4+5), ... etc. Or a(n) = (T(n))*(T(n)+n)*(T(n)+2n)*(T(n)+3n)*... n terms. where T(n) = n(n+1)/2 given by A000217.

A092958

a(1) = 1, a(2) = (1+2)*(2+3), a(3) = (1+2+3)*(2+3+4)*(3+4+5), ... etc. Or a(n) = (T(n))*(T(n)+n)*(T(n)+2n)*(T(n)+3n)*... n terms. where T(n) = n(n+1)/2 given by A000217.

Terms

    a(0) =1a(1) =15a(2) =648a(3) =55440a(4) =7875000a(5) =1674728055a(6) =498078806400

External references