Numbers k such that 5 and 7 occur juxtaposed in the base-10 representation of k but not of k+1.

Terms

a(0) =57a(1) =75a(2) =157a(3) =175a(4) =257a(5) =275a(6) =357a(7) =375a(8) =457a(9) =475a(10) =557a(11) =579a(12) =657a(13) =675a(14) =759a(15) =775a(16) =857a(17) =875a(18) =957a(19) =975a(20) =1057a(21) =1075a(22) =1157a(23) =1175a(24) =1257a(25) =1275a(26) =1357a(27) =1375a(28) =1457a(29) =1475