a(n) = (2*n+1)^2*n!.

Terms

a(0) =1a(1) =9a(2) =50a(3) =294a(4) =1944a(5) =14520a(6) =121680a(7) =1134000a(8) =11652480a(9) =130999680a(10) =1600300800a(11) =21115987200a(12) =299376000000