A025707 Index of 5^n within sequence of numbers of form 5^i*6^j.

1, 2, 4, 7, 11, 16, 22, 29, 37, 46, 55, 65, 76, 88, 101, 115, 130, 146, 163, 181, 199, 218, 238, 259, 281, 304, 328, 353, 379, 406, 433, 461, 490, 520, 551, 583, 616, 650, 685, 721, 757, 794, 832, 871, 911, 952, 994, 1037, 1081, 1126, 1171, 1217, 1264, 1312, 1361