A043145 Numbers n such that 2 and 6 occur juxtaposed in the base 7 representation of n but not of n-1.

20, 44, 69, 93, 118, 140, 167, 191, 216, 240, 265, 289, 308, 338, 363, 387, 412, 436, 461, 483, 510, 534, 559, 583, 608, 632, 651, 681, 706, 730, 755, 779, 804, 826, 853, 877, 902, 926, 951, 975, 980, 1049, 1073, 1098, 1122