a(n) = floor(n*(n - 1)*(n - 2)/32).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =1a(6) =3a(7) =6a(8) =10a(9) =15a(10) =22a(11) =30a(12) =41a(13) =53a(14) =68a(15) =85a(16) =105a(17) =127a(18) =153a(19) =181a(20) =213a(21) =249a(22) =288a(23) =332a(24) =379a(25) =431a(26) =487a(27) =548a(28) =614a(29) =685