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

Terms

a(0) =0a(1) =1a(2) =8a(3) =26a(4) =63a(5) =124a(6) =208a(7) =335a(8) =504a(9) =702a(10) =973a(11) =1304a(12) =1664a(13) =2133a(14) =2680a(15) =3250a(16) =3971a(17) =4788a(18) =5616a(19) =6643a(20) =7784a(21) =8918a(22) =10305a(23) =11824a(24) =13312a(25) =15113a(26) =17064a(27) =18954a(28) =21223a(29) =23660