If n mod 2 = 0 then a(n) = n^4/4 - 2*n^2 + 3*n; otherwise, a(n) = n^4/4 - 2*n^2 + 3*n - 5/4.

Terms

a(0) =0a(1) =0a(2) =2a(3) =10a(4) =44a(5) =120a(6) =270a(7) =522a(8) =920a(9) =1504a(10) =2330a(11) =3450a(12) =4932a(13) =6840a(14) =9254a(15) =12250a(16) =15920a(17) =20352a(18) =25650a(19) =31914a(20) =39260a(21) =47800a(22) =57662a(23) =68970a(24) =81864a(25) =96480a(26) =112970a(27) =131482a(28) =152180a(29) =175224