A044174 Numbers n such that string 5,1 occurs in the base 7 representation of n but not of n-1.

36, 85, 134, 183, 232, 252, 281, 330, 379, 428, 477, 526, 575, 595, 624, 673, 722, 771, 820, 869, 918, 938, 967, 1016, 1065, 1114, 1163, 1212, 1261, 1281, 1310, 1359, 1408, 1457, 1506, 1555, 1604, 1624, 1653, 1702, 1751, 1764