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

Terms

a(0) =-3a(1) =5a(2) =57a(3) =237a(4) =677a(5) =1557a(6) =3105a(7) =5597a(8) =9357a(9) =14757a(10) =22217a(11) =32205a(12) =45237a(13) =61877a(14) =82737a(15) =108477a(16) =139805a(17) =177477a(18) =222297a(19) =275117a(20) =336837a(21) =408405a(22) =490817a(23) =585117a(24) =692397a(25) =813797a(26) =950505a(27) =1103757a(28) =1274837a(29) =1465077