Numbers whose base-7 representation has the same number of 0's and 1's.

Terms

a(0) =2a(1) =3a(2) =4a(3) =5a(4) =6a(5) =7a(6) =16a(7) =17a(8) =18a(9) =19a(10) =20a(11) =23a(12) =24a(13) =25a(14) =26a(15) =27a(16) =30a(17) =31a(18) =32a(19) =33a(20) =34a(21) =37a(22) =38a(23) =39a(24) =40a(25) =41a(26) =44a(27) =45a(28) =46a(29) =47