Numbers whose base-10 representation has the same nonzero number of 7's and 8's.

Terms

a(0) =78a(1) =87a(2) =178a(3) =187a(4) =278a(5) =287a(6) =378a(7) =387a(8) =478a(9) =487a(10) =578a(11) =587a(12) =678a(13) =687a(14) =708a(15) =718a(16) =728a(17) =738a(18) =748a(19) =758a(20) =768a(21) =780a(22) =781a(23) =782a(24) =783a(25) =784a(26) =785a(27) =786a(28) =789a(29) =798