Numbers k such that 7 and 9 occur juxtaposed in the base-10 representation of k but not of k-1.

Terms

a(0) =79a(1) =97a(2) =179a(3) =197a(4) =279a(5) =297a(6) =379a(7) =397a(8) =479a(9) =497a(10) =579a(11) =597a(12) =679a(13) =697a(14) =779a(15) =790a(16) =879a(17) =897a(18) =970a(19) =997a(20) =1079a(21) =1097a(22) =1179a(23) =1197a(24) =1279a(25) =1297a(26) =1379a(27) =1397a(28) =1479a(29) =1497