A043959 Numbers n such that 6 and 7 occur juxtaposed in the base 8 representation of n but not of n+1.

55, 62, 119, 126, 183, 190, 247, 254, 311, 318, 375, 382, 447, 503, 510, 567, 574, 631, 638, 695, 702, 759, 766, 823, 830, 887, 894, 959, 1015, 1022, 1079, 1086, 1143, 1150, 1207, 1214, 1271, 1278, 1335, 1342, 1399, 1406, 1471