Numbers whose base-7 representation has the same nonzero number of 0's and 4's.

Terms

a(0) =28a(1) =53a(2) =77a(3) =102a(4) =126a(5) =151a(6) =175a(7) =197a(8) =198a(9) =199a(10) =201a(11) =202a(12) =203a(13) =210a(14) =217a(15) =231a(16) =238a(17) =249a(18) =273a(19) =298a(20) =322a(21) =354a(22) =361a(23) =368a(24) =372a(25) =373a(26) =374a(27) =376a(28) =377a(29) =382