A025709 Index of 5^n within sequence of numbers of form 5^i*8^j.
1, 2, 4, 7, 11, 15, 20, 26, 33, 40, 48, 57, 67, 78, 89, 101, 114, 128, 142, 157, 173, 190, 208, 226, 245, 265, 286, 307, 329, 352, 376, 400, 425, 451, 478, 506, 534, 563, 593, 624, 655, 687, 720, 754, 789, 824, 860, 897, 935, 973, 1012, 1052, 1093, 1135, 1177, 1220
Offset: 1
Keywords
Programs
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PARI
a(n)=my(N=1); n+1+sum(i=1, n, logint(N*=5, 8)); \\ Charles R Greathouse IV, Jan 16 2018
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PARI
first(n)=my(s, N=1/5); vector(n+1, i, s+=logint(N*=5, 8)+1) \\ Charles R Greathouse IV, Jan 16 2018
Comments