A043383 Numbers n such that number of 3's in base 6 is 3.

129, 345, 561, 669, 705, 741, 759, 765, 771, 774, 775, 776, 778, 779, 783, 789, 813, 849, 993, 1209, 1425, 1641, 1857, 1965, 2001, 2037, 2055, 2061, 2067, 2070, 2071, 2072, 2074, 2075, 2079, 2085, 2109, 2145, 2289, 2505