A039525 Numbers n such that representation in base 12 has same nonzero number of 3's and 6's.

42, 75, 186, 219, 330, 363, 438, 450, 462, 486, 498, 504, 505, 506, 508, 509, 511, 512, 513, 514, 515, 522, 534, 546, 558, 570, 618, 651, 762, 795, 867, 879, 891, 900, 901, 902, 904, 905, 907, 908, 909, 910, 911, 915, 927, 951, 963, 975, 987, 999, 1050