A044423 Numbers n such that string 9,1 occurs in the base 10 representation of n but not of n-1.

91, 191, 291, 391, 491, 591, 691, 791, 891, 910, 991, 1091, 1191, 1291, 1391, 1491, 1591, 1691, 1791, 1891, 1910, 1991, 2091, 2191, 2291, 2391, 2491, 2591, 2691, 2791, 2891, 2910, 2991, 3091, 3191, 3291, 3391, 3491, 3591