a(1) = 3, a(n) = a(n-1) + 4*(a(n-1)-floor(a(n-1)^(1/3))^3).

Terms

a(0) =3a(1) =11a(2) =23a(3) =83a(4) =159a(5) =295a(6) =611a(7) =1007a(8) =1035a(9) =1175a(10) =1875a(11) =2463a(12) =3527a(13) =4135a(14) =4291a(15) =5071a(16) =5703a(17) =8863a(18) =12315a(19) =12907a(20) =15867a(21) =16835a(22) =21675a(23) =29643a(24) =40215a(25) =43859a(26) =47795a(27) =52351a(28) =59143a(29) =76227