A044178 Numbers n such that string 5,5 occurs in the base 7 representation of n but not of n-1.

40, 89, 138, 187, 236, 280, 334, 383, 432, 481, 530, 579, 623, 677, 726, 775, 824, 873, 922, 966, 1020, 1069, 1118, 1167, 1216, 1265, 1309, 1363, 1412, 1461, 1510, 1559, 1608, 1652, 1706, 1755, 1804, 1853, 1902, 1951, 1960