A025648 Exponent of 4 (value of i) in n-th number of form 4^i*7^j.

0, 1, 0, 2, 1, 0, 3, 2, 1, 4, 0, 3, 2, 5, 1, 4, 0, 3, 6, 2, 5, 1, 4, 7, 0, 3, 6, 2, 5, 8, 1, 4, 7, 0, 3, 6, 9, 2, 5, 8, 1, 4, 7, 0, 10, 3, 6, 9, 2, 5, 8, 1, 11, 4, 7, 0, 10, 3, 6, 9, 2, 12, 5, 8, 1, 11, 4, 7, 0, 10, 3, 13, 6, 9, 2, 12, 5, 8, 1, 11, 4, 14, 7, 0, 10, 3, 13, 6, 9, 2, 12, 5, 15, 8, 1, 11, 4, 14, 7