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

Terms

a(0) =0a(1) =0a(2) =4a(3) =13a(4) =32a(5) =62a(6) =108a(7) =171a(8) =256a(9) =364a(10) =500a(11) =665a(12) =864a(13) =1098a(14) =1372a(15) =1687a(16) =2048a(17) =2456a(18) =2916a(19) =3429a(20) =4000a(21) =4630a(22) =5324a(23) =6083a(24) =6912a(25) =7812a(26) =8788a(27) =9841a(28) =10976a(29) =12194