a(n) = binomial(9*n+3, n)/(3*n+1).

A234506

a(n) = binomial(9*n+3, n)/(3*n+1).

Terms

    a(0) =1a(1) =3a(2) =30a(3) =406a(4) =6327a(5) =107019a(6) =1909908a(7) =35399520a(8) =674842149a(9) =13147742322a(10) =260626484118

External references