A062524 7^a(n) is smallest nonnegative power of 7 containing the string 'n'.

4, 0, 4, 3, 2, 7, 5, 1, 5, 2, 13, 6, 12, 12, 19, 15, 5, 6, 19, 11, 12, 22, 14, 7, 4, 30, 11, 23, 10, 16, 14, 19, 11, 16, 3, 7, 9, 19, 12, 17, 4, 12, 27, 3, 18, 21, 32, 10, 8, 2, 15, 17, 10, 9, 7, 21, 15, 8, 21, 18, 9, 15, 18, 17, 6, 27, 20, 11, 5, 16, 33, 27, 12, 11, 11, 10