Surprised nobody corrected me when I said the NCAA used to only allow one and two digit numbers with 1-5 used. Actually it was 0-5 but you couldn't use 0 as a first number or alone.
1, 2, 3, 4, 5, 10, 11, 12, 13, 14, 15, 20, 21, 22, 23, 24, 25, 30, 31, 32, 33, 34, 35, 40, 41, 42, 43, 44, 45...