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A022335
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Index of 2^n within sequence of numbers of form 2^i * 5^j.
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2
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1, 2, 3, 5, 7, 10, 13, 17, 21, 25, 30, 35, 41, 47, 54, 61, 68, 76, 84, 93, 102, 112, 122, 132, 143, 154, 166, 178, 191, 204, 217, 231, 245, 260, 275, 291, 307, 323, 340, 357, 375, 393, 412, 431, 450, 470, 490, 511, 532, 554, 576, 598, 621, 644, 668, 692, 717, 742, 767, 793
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OFFSET
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0,2
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COMMENTS
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LINKS
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FORMULA
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a(n) = Sum_{i=0..n} (1 + floor(log_5(2^i))). - Michel Marcus, Oct 02 2013
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MATHEMATICA
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Table[1 + Sum[Ceiling[j*Log[5, 2]], {j, i}], {i, 0, 59}] (* Michael De Vlieger, Feb 08 2023 *)
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PROG
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(PARI) a(n) = sum(i=0, n, 1 + floor(log(2^i)/log(5))); \\ Michel Marcus, Oct 02 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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