Floor(n^3/8).

Terms

a(0) =0a(1) =0a(2) =1a(3) =3a(4) =8a(5) =15a(6) =27a(7) =42a(8) =64a(9) =91a(10) =125a(11) =166a(12) =216a(13) =274a(14) =343a(15) =421a(16) =512a(17) =614a(18) =729a(19) =857a(20) =1000a(21) =1157a(22) =1331a(23) =1520a(24) =1728a(25) =1953a(26) =2197a(27) =2460a(28) =2744a(29) =3048