Numbers whose base-10 representation has the same nonzero number of 6's and 7's.

Terms

a(0) =67a(1) =76a(2) =167a(3) =176a(4) =267a(5) =276a(6) =367a(7) =376a(8) =467a(9) =476a(10) =567a(11) =576a(12) =607a(13) =617a(14) =627a(15) =637a(16) =647a(17) =657a(18) =670a(19) =671a(20) =672a(21) =673a(22) =674a(23) =675a(24) =678a(25) =679a(26) =687a(27) =697a(28) =706a(29) =716