A044790 Numbers n such that string 7,7 occurs in the base 10 representation of n but not of n+1.

77, 177, 277, 377, 477, 577, 677, 779, 877, 977, 1077, 1177, 1277, 1377, 1477, 1577, 1677, 1779, 1877, 1977, 2077, 2177, 2277, 2377, 2477, 2577, 2677, 2779, 2877, 2977, 3077, 3177, 3277, 3377, 3477, 3577, 3677, 3779, 3877