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

A076151

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

Terms

    a(0) =1a(1) =8a(2) =110a(3) =2184a(4) =57120a(5) =1860480a(6) =72681840a(7) =3315312000a(8) =173059286400

External references