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Search: id:A131538
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| A131538 |
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Least power of 2 having exactly n consecutive 4's in its decimal representation. |
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+0
1
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| 2, 18, 44, 192, 315, 3396, 8556, 13327, 81785, 279267
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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a(3)=44 because 2^44(i.e. 17592186044416) is the smallest power of 2 to contain a run of 3 consecutive fours in its decimal form.
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MATHEMATICA
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a = ""; Do[ a = StringJoin[a, "4"]; b = StringJoin[a, "4"]; k = 1; While[ StringPosition[ ToString[2^k], a] == {} || StringPosition[ ToString[2^k], b] != {}, k++ ]; Print[k], {n, 1, 10} ]
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CROSSREFS
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Sequence in context: A050594 A098857 A072278 this_sequence A009820 A126909 A139268
Adjacent sequences: A131535 A131536 A131537 this_sequence A131539 A131540 A131541
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KEYWORD
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more,nonn,base
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AUTHOR
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Shyam Sunder Gupta (guptass(AT)rediffmail.com), Aug 26 2007
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