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A131541
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Least power of 2 having exactly n consecutive 7's in its decimal representation.
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1
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15, 27, 24, 181, 317, 2309, 972, 25264, 131979, 279275, 279269, 1727605, 6030752, 8760853, 77235364
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OFFSET
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1,1
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LINKS
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Popular Computing (Calabasas, CA), Two Tables, Vol. 1, (No. 9, Dec 1973), page PC9-16.
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EXAMPLE
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a(3)=24 because 2^24(i.e. 16777216) is the smallest power of 2 to contain a run of 3 consecutive sevens in its decimal form.
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MATHEMATICA
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a = ""; Do[ a = StringJoin[a, "7"]; b = StringJoin[a, "7"]; 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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KEYWORD
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more,nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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