a(n) = 2*f(2*n)/(f(n)*f(n+2)) where f = A003266.

A372949

a(n) = 2*f(2*n)/(f(n)*f(n+2)) where f = A003266.

Terms

    a(0) =1a(1) =2a(2) =8a(3) =91a(4) =2618a(5) =199716a(6) =39690618a(7) =20689636692

External references