Numbers whose base-4 representation has the same number of 0's as 3's.

Terms

a(0) =1a(1) =2a(2) =5a(3) =6a(4) =9a(5) =10a(6) =12a(7) =19a(8) =21a(9) =22a(10) =25a(11) =26a(12) =28a(13) =35a(14) =37a(15) =38a(16) =41a(17) =42a(18) =44a(19) =49a(20) =50a(21) =52a(22) =56a(23) =71a(24) =75a(25) =77a(26) =78a(27) =83a(28) =85a(29) =86