A025741 Index of 10^n within sequence of numbers of form 3^i*10^j.

1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 145, 171, 199, 229, 261, 295, 331, 369, 409, 451, 496, 543, 592, 643, 696, 751, 808, 867, 928, 991, 1056, 1124, 1194, 1266, 1340, 1416, 1494, 1574, 1656, 1740, 1826, 1915, 2006, 2099, 2194, 2291, 2390, 2491, 2594, 2699