A043518 Numbers n such that number of 7's in base 10 is 2.

77, 177, 277, 377, 477, 577, 677, 707, 717, 727, 737, 747, 757, 767, 770, 771, 772, 773, 774, 775, 776, 778, 779, 787, 797, 877, 977, 1077, 1177, 1277, 1377, 1477, 1577, 1677, 1707, 1717, 1727, 1737, 1747, 1757, 1767, 1770, 1771