A025743 Index of 10^n within sequence of numbers of form 5^i*10^j.

1, 3, 6, 11, 17, 25, 34, 45, 57, 70, 85, 101, 119, 138, 159, 181, 204, 229, 255, 283, 312, 343, 375, 408, 443, 479, 517, 556, 597, 639, 682, 727, 773, 821, 870, 921, 973, 1026, 1081, 1137, 1195, 1254, 1315, 1377, 1440, 1505, 1571, 1639, 1708, 1779, 1851, 1924