Numbers whose base-10 representation has the same nonzero number of 5's and 7's.

Terms

a(0) =57a(1) =75a(2) =157a(3) =175a(4) =257a(5) =275a(6) =357a(7) =375a(8) =457a(9) =475a(10) =507a(11) =517a(12) =527a(13) =537a(14) =547a(15) =567a(16) =570a(17) =571a(18) =572a(19) =573a(20) =574a(21) =576a(22) =578a(23) =579a(24) =587a(25) =597a(26) =657a(27) =675a(28) =705a(29) =715