a(n) = sigma(2*n) * binomial(2*n,n)/2, for n >= 1.

Terms

a(0) =3a(1) =21a(2) =120a(3) =525a(4) =2268a(5) =12936a(6) =41184a(7) =199485a(8) =948090a(9) =3879876a(10) =12697776a(11) =81124680a(12) =218412600a(13) =1123264800a(14) =5584230720a(15) =18934032285a(16) =63007367940a(17) =412918656150