Numbers whose base-7 representation has the same number of 1's and 4's.

Terms

a(0) =0a(1) =2a(2) =3a(3) =5a(4) =6a(5) =11a(6) =14a(7) =16a(8) =17a(9) =19a(10) =20a(11) =21a(12) =23a(13) =24a(14) =26a(15) =27a(16) =29a(17) =35a(18) =37a(19) =38a(20) =40a(21) =41a(22) =42a(23) =44a(24) =45a(25) =47a(26) =48a(27) =53a(28) =67a(29) =74