A001161 Numbers containing an even number of letters.

0, 4, 5, 9, 11, 12, 13, 14, 18, 19, 20, 24, 25, 29, 30, 34, 35, 39, 41, 42, 43, 46, 47, 48, 51, 52, 53, 56, 57, 58, 61, 62, 63, 66, 67, 68, 71, 72, 73, 76, 77, 78, 80, 84, 85, 89, 90, 94, 95, 99