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

Terms

a(0) =0a(1) =3a(2) =42a(3) =390a(4) =2940a(5) =19530a(6) =119196a(7) =684684a(8) =3758040a(9) =19909890a(10) =102539580a(11) =516023508a(12) =2547314952a(13) =12371513700a(14) =59252218200a(15) =280374917400