a(n) = n^7*(9*n+7)/2.

Terms

a(0) =0a(1) =8a(2) =1600a(3) =37179a(4) =352256a(5) =2031250a(6) =8538048a(7) =28824005a(8) =82837504a(9) =210450636a(10) =485000000a(11) =1032820063a(12) =2060328960a(13) =3890408054a(14) =7009998016a(15) =12131015625a(16) =20266876928a(17) =32827093840a(18) =51732592704a(19) =79554584771a(20) =119680000000a(21) =176506677018a(22) =255671683520a(23) =364316322829