A025477 Exponent of n-th nontrivial prime power (A025475).

0, 2, 3, 2, 4, 2, 3, 5, 2, 6, 4, 2, 3, 7, 2, 5, 8, 2, 3, 2, 9, 2, 4, 6, 2, 2, 10, 3, 2, 2, 2, 11, 7, 3, 2, 4, 2, 5, 2, 2, 12, 2, 3, 2, 2, 2, 8, 3, 2, 2, 13, 2, 2, 2, 2, 2, 3, 2, 4, 6, 2, 14, 5, 2, 2, 2, 9, 2, 2, 3, 2, 2, 2, 4, 3, 2, 2, 2, 15, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 10, 2, 16, 2, 3, 2, 2, 2, 2, 7, 2, 3, 2