(2n^7 + 4n^6 - n^5 - 4n^4 - n^3) / 24.

Terms

a(0) =0a(1) =0a(2) =17a(3) =279a(4) =1960a(5) =8875a(6) =30555a(7) =87122a(8) =216384a(9) =483570a(10) =994125a(11) =1909985a(12) =3469752a(13) =6013189a(14) =10010455a(15) =16096500a(16) =25111040a(17) =38144532a(18) =56590569a(19) =82205115a(20) =117173000a(21) =164182095a(22) =226505587a(23) =308092774a(24) =413668800a(25) =548843750a(26) =720231525a(27) =935578917a(28) =1203905304