A025740 Index of 10^n within sequence of numbers of form 2^i*10^j.

1, 5, 12, 22, 36, 53, 73, 97, 124, 154, 188, 225, 265, 309, 356, 406, 460, 517, 577, 641, 708, 778, 852, 929, 1009, 1093, 1180, 1270, 1364, 1461, 1561, 1664, 1771, 1881, 1994, 2111, 2231, 2354, 2481, 2611, 2744, 2881, 3021, 3164, 3311, 3461, 3614, 3771, 3931