a(n) = (1/24)*n*((4*n + 3)*(2*n^2 + 1) - 3*(-1)^n).

Terms

a(0) =0a(1) =1a(2) =8a(3) =36a(4) =104a(5) =245a(6) =492a(7) =896a(8) =1504a(9) =2385a(10) =3600a(11) =5236a(12) =7368a(13) =10101a(14) =13524a(15) =17760a(16) =22912a(17) =29121a(18) =36504a(19) =45220a(20) =55400a(21) =67221a(22) =80828a(23) =96416a(24) =114144a(25) =134225a(26) =156832a(27) =182196a(28) =210504a(29) =242005