a(n) = (6*n^4 + 30*n^3 - 20*n^2 + 14)*n/30 + (n mod 2).

Terms

a(0) =0a(1) =2a(2) =18a(3) =114a(4) =420a(5) =1170a(6) =2710a(7) =5538a(8) =10312a(9) =17890a(10) =29338a(11) =45970a(12) =69356a(13) =101362a(14) =144158a(15) =200258a(16) =272528a(17) =364226a(18) =479010a(19) =620978a(20) =794676a(21) =1005138a(22) =1257894a(23) =1559010a(24) =1915096a(25) =2333346a(26) =2821546a(27) =3388114a(28) =4042108a(29) =4793266