A043927 Numbers n such that 3 and 5 occur juxtaposed in the base 7 representation of n but not of n+1.

26, 38, 75, 87, 124, 136, 173, 188, 222, 234, 272, 283, 320, 332, 369, 381, 418, 430, 467, 479, 516, 531, 565, 577, 615, 626, 663, 675, 712, 724, 761, 773, 810, 822, 859, 874, 908, 920, 958, 969, 1006, 1018, 1055, 1067, 1104