a(n) = (n+1)*(9-9*n+5*n^2-n^3).

Terms

a(0) =9a(1) =8a(2) =9a(3) =0a(4) =-55a(5) =-216a(6) =-567a(7) =-1216a(8) =-2295a(9) =-3960a(10) =-6391a(11) =-9792a(12) =-14391a(13) =-20440a(14) =-28215a(15) =-38016a(16) =-50167a(17) =-65016a(18) =-82935a(19) =-104320a(20) =-129591a(21) =-159192a(22) =-193591a(23) =-233280a(24) =-278775a(25) =-330616a(26) =-389367a(27) =-455616a(28) =-529975a(29) =-613080