a(n) = ceiling((n^3)/2).

Terms

a(0) =0a(1) =1a(2) =4a(3) =14a(4) =32a(5) =63a(6) =108a(7) =172a(8) =256a(9) =365a(10) =500a(11) =666a(12) =864a(13) =1099a(14) =1372a(15) =1688a(16) =2048a(17) =2457a(18) =2916a(19) =3430a(20) =4000a(21) =4631a(22) =5324a(23) =6084a(24) =6912a(25) =7813a(26) =8788a(27) =9842a(28) =10976a(29) =12195