a(n) = (72 - 258*n + 601*n^2 - 264*n^3 + 33*n^4)/4.

Terms

a(0) =18a(1) =46a(2) =94a(3) =63a(4) =52a(5) =358a(6) =1476a(7) =4099a(8) =9118a(9) =17622a(10) =30898a(11) =50431a(12) =77904a(13) =115198a(14) =164392a(15) =227763a(16) =307786a(17) =407134a(18) =528678a(19) =675487a(20) =850828a(21) =1058166a(22) =1301164a(23) =1583683a(24) =1909782a(25) =2283718a(26) =2709946a(27) =3193119a(28) =3738088a(29) =4349902