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A063611
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Smallest k such that 7^k has exactly n 5's in its decimal representation.
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0
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1, 7, 15, 27, 21, 49, 55, 47, 51, 87, 85, 107, 75, 99, 61, 149, 138, 133, 171, 135, 165, 237, 209, 197, 269, 221, 232, 219, 277, 248, 258, 306, 271, 264, 357, 296, 310, 347, 354, 260, 342, 374, 407, 425, 362, 457, 485, 480, 486, 488, 492
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OFFSET
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0,2
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LINKS
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MATHEMATICA
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a = {}; Do[k = 1; While[ Count[ IntegerDigits[7^k], 5] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
Join[{1}, With[{p7=7^Range[0, 500]}, Flatten[Table[Position[p7, _?(DigitCount[ #, 10, 5]==n&), {1}, 1], {n, 50}]]-1]] (* Harvey P. Dale, Sep 17 2013 *)
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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