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

Terms

a(0) =0a(1) =0a(2) =0a(3) =6a(4) =24a(5) =60a(6) =120a(7) =210a(8) =336a(9) =504a(10) =720a(11) =990a(12) =1320a(13) =1716a(14) =2184a(15) =2730a(16) =3360a(17) =4080a(18) =4896a(19) =5814a(20) =6840a(21) =7980a(22) =9240a(23) =10626a(24) =12144a(25) =13800a(26) =15600a(27) =17550a(28) =19656a(29) =21924