A043240 Numbers n such that 3 and 4 occur juxtaposed in the base 10 representation of n but not of n-1.

34, 43, 134, 143, 234, 243, 334, 340, 430, 443, 534, 543, 634, 643, 734, 743, 834, 843, 934, 943, 1034, 1043, 1134, 1143, 1234, 1243, 1334, 1340, 1430, 1443, 1534, 1543, 1634, 1643, 1734, 1743, 1834, 1843, 1934, 1943, 2034