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A063526
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Smallest k such that 2^k has exactly n 5's in its decimal representation.
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9
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1, 8, 16, 39, 41, 68, 131, 108, 142, 178, 198, 201, 167, 215, 283, 344, 367, 318, 404, 428, 312, 461, 441, 556, 506, 562, 536, 716, 652, 679, 733, 690, 575, 807, 627, 949, 811, 867, 932, 1035, 1003, 1088, 893, 1112, 1193, 1080, 1127, 1094, 1016, 1283
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OFFSET
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0,2
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LINKS
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Harry J. Smith, Table of n, a(n) for n = 0..150
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MATHEMATICA
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a = {}; Do[k = 1; While[ Count[ IntegerDigits[2^k], 5] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
Join[{1}, Flatten[With[{pwrs=DigitCount[#, 10, 5]&/@(2^Range[0, 1300])}, Table[Position[pwrs, n, 1, 1], {n, 50}]]]-1] (* Harvey P. Dale, Jan 28 2013 *)
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PROG
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(PARI) a(n)={my(k=1); while(n<>#select(d->d==5, digits(2^k)), k++); k} \\ Harry J. Smith, Aug 25 2009, Andrew Howroyd, Jun 26 2018
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CROSSREFS
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Cf. A063115, A063426, A063429, A063430, A063540, A063552, A063553, A063554.
Sequence in context: A054301 A197773 A057584 * A156331 A269513 A024700
Adjacent sequences: A063523 A063524 A063525 * A063527 A063528 A063529
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KEYWORD
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base,nonn
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AUTHOR
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Robert G. Wilson v, Aug 10 2001
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EXTENSIONS
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Name corrected by Jon E. Schoenfield, Jun 25 2018
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STATUS
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approved
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