Numbers whose base-10 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) =9a(8) =13a(9) =20a(10) =22a(11) =24a(12) =25a(13) =26a(14) =27a(15) =28a(16) =29a(17) =31a(18) =40a(19) =42a(20) =44a(21) =45a(22) =46a(23) =47a(24) =48a(25) =49a(26) =50a(27) =52a(28) =54a(29) =55