A039403 Numbers whose base-10 representation has the same nonzero number of 1's and 3's.

13, 31, 103, 123, 130, 132, 134, 135, 136, 137, 138, 139, 143, 153, 163, 173, 183, 193, 213, 231, 301, 310, 312, 314, 315, 316, 317, 318, 319, 321, 341, 351, 361, 371, 381, 391, 413, 431, 513, 531, 613, 631, 713, 731, 813, 831, 913, 931, 1003, 1023