A043151 Numbers n such that 5 and 6 occur juxtaposed in the base 7 representation of n but not of n-1.

41, 47, 90, 96, 139, 145, 188, 194, 237, 243, 286, 329, 341, 384, 390, 433, 439, 482, 488, 531, 537, 580, 586, 629, 672, 684, 727, 733, 776, 782, 825, 831, 874, 880, 923, 929, 972, 1015, 1027, 1070, 1076, 1119, 1125, 1168, 1174