a(n) = floor(8*n^3/27).

Terms

a(0) =0a(1) =0a(2) =2a(3) =8a(4) =18a(5) =37a(6) =64a(7) =101a(8) =151a(9) =216a(10) =296a(11) =394a(12) =512a(13) =650a(14) =813a(15) =1000a(16) =1213a(17) =1455a(18) =1728a(19) =2032a(20) =2370a(21) =2744a(22) =3154a(23) =3605a(24) =4096a(25) =4629a(26) =5207a(27) =5832a(28) =6504a(29) =7226