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

Terms

a(0) =0a(1) =2a(2) =18a(3) =120a(4) =700a(5) =3780a(6) =19404a(7) =96096a(8) =463320a(9) =2187900a(10) =10161580a(11) =46558512a(12) =210924168a(13) =946454600a(14) =4212243000a(15) =18614102400a(16) =81746933040a(17) =357041751660