A033006 Every run of digits of n in base 6 has length 2.

9, 18, 27, 36, 45, 54, 63, 576, 594, 603, 612, 621, 630, 639, 1152, 1161, 1179, 1188, 1197, 1206, 1215, 1728, 1737, 1746, 1764, 1773, 1782, 1791, 2304, 2313, 2322, 2331, 2349, 2358, 2367, 2880, 2889, 2898, 2907, 2916, 2934