a(n) = floor(n^3/3).

Terms

a(0) =0a(1) =0a(2) =2a(3) =9a(4) =21a(5) =41a(6) =72a(7) =114a(8) =170a(9) =243a(10) =333a(11) =443a(12) =576a(13) =732a(14) =914a(15) =1125a(16) =1365a(17) =1637a(18) =1944a(19) =2286a(20) =2666a(21) =3087a(22) =3549a(23) =4055a(24) =4608a(25) =5208a(26) =5858a(27) =6561a(28) =7317a(29) =8129