A045124 Numbers n with property that in base 4 representation the numbers of 1's and 3's are 3 and 0, respectively.

21, 69, 81, 84, 86, 89, 101, 149, 261, 273, 276, 278, 281, 293, 321, 324, 326, 329, 336, 338, 344, 346, 353, 356, 358, 361, 389, 401, 404, 406, 409, 421, 533, 581, 593, 596, 598, 601, 613, 661, 1029, 1041, 1044, 1046, 1049, 1061