a(n) = (n + 1)*(n^2 + 2)*(n^3 + 3)*(n^4 + 4)/4!.

Terms

a(0) =1a(1) =5a(2) =165a(3) =4675a(4) =65325a(5) =543456a(6) =3155425a(7) =14146210a(8) =52259625a(9) =166192975a(10) =469090061a(11) =1201490445a(12) =2839166005a(13) =6268589250a(14) =13060542825a(15) =25881747316a(16) =49095506065a(17) =89615392425a(18) =158091087925a(19) =270522770375a(20) =450420100221a(21) =731644012660