a(n) = binomial(6*n,3*n)*binomial(2*n,n).

A275655

a(n) = binomial(6*n,3*n)*binomial(2*n,n).

Terms

    a(0) =1a(1) =40a(2) =5544a(3) =972400a(4) =189290920a(5) =39089615040

External references