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

Terms

a(0) =0a(1) =0a(2) =5a(3) =18a(4) =42a(5) =80a(6) =135a(7) =210a(8) =308a(9) =432a(10) =585a(11) =770a(12) =990a(13) =1248a(14) =1547a(15) =1890a(16) =2280a(17) =2720a(18) =3213a(19) =3762a(20) =4370a(21) =5040a(22) =5775a(23) =6578a(24) =7452a(25) =8400a(26) =9425a(27) =10530a(28) =11718a(29) =12992