Numbers k such that 3 and 4 occur juxtaposed in the base-10 representation of k but not of k+1.

Terms

a(0) =34a(1) =43a(2) =134a(3) =143a(4) =234a(5) =243a(6) =334a(7) =349a(8) =439a(9) =443a(10) =534a(11) =543a(12) =634a(13) =643a(14) =734a(15) =743a(16) =834a(17) =843a(18) =934a(19) =943a(20) =1034a(21) =1043a(22) =1134a(23) =1143a(24) =1234a(25) =1243a(26) =1334a(27) =1349a(28) =1439a(29) =1443