Numbers whose base-4 representation has the same number of 0's and 2's.

Terms

a(0) =1a(1) =3a(2) =5a(3) =7a(4) =8a(5) =13a(6) =15a(7) =18a(8) =21a(9) =23a(10) =24a(11) =29a(12) =31a(13) =33a(14) =35a(15) =36a(16) =44a(17) =50a(18) =53a(19) =55a(20) =56a(21) =61a(22) =63a(23) =70a(24) =73a(25) =75a(26) =78a(27) =82a(28) =85a(29) =87