Numbers with no 1's in their base 4 expansion.

Terms

a(0) =0a(1) =2a(2) =3a(3) =8a(4) =10a(5) =11a(6) =12a(7) =14a(8) =15a(9) =32a(10) =34a(11) =35a(12) =40a(13) =42a(14) =43a(15) =44a(16) =46a(17) =47a(18) =48a(19) =50a(20) =51a(21) =56a(22) =58a(23) =59a(24) =60a(25) =62a(26) =63a(27) =128a(28) =130a(29) =131