Numbers whose base-9 representation has the same number of 1's and 3's.

Terms

a(0) =0a(1) =2a(2) =4a(3) =5a(4) =6a(5) =7a(6) =8a(7) =12a(8) =18a(9) =20a(10) =22a(11) =23a(12) =24a(13) =25a(14) =26a(15) =28a(16) =36a(17) =38a(18) =40a(19) =41a(20) =42a(21) =43a(22) =44a(23) =45a(24) =47a(25) =49a(26) =50a(27) =51a(28) =52a(29) =53