a(n) = binomial(n^2 + 3*n, n) / (n+1)^2.

A182316

a(n) = binomial(n^2 + 3*n, n) / (n+1)^2.

Terms

    a(0) =1a(1) =1a(2) =5a(3) =51a(4) =819a(5) =18278a(6) =527085a(7) =18730855a(8) =793542167a(9) =39113958819

External references