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A034054
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Numbers with multiplicative digital root value 7.
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13
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7, 17, 71, 117, 171, 711, 1117, 1171, 1711, 7111, 11117, 11171, 11711, 17111, 71111, 111117, 111171, 111711, 117111, 171111, 711111, 1111117, 1111171, 1111711, 1117111, 1171111, 1711111, 7111111, 11111117, 11111171, 11111711, 11117111
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OFFSET
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1,1
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COMMENTS
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Numbers with one 7, and zero or more 1s. - Daniel Forgues, Oct 09 2011
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LINKS
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Table of n, a(n) for n=1..32.
Eric Weisstein's World of Mathematics, Multiplicative Digital Root
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FORMULA
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There are n(n+1)/2 elements up to 10^n, so a(n) is about 10^sqrt(2n).
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CROSSREFS
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Cf. A031347.
Cf. A034048, A002275, A034049, A034050, A034051, A034052, A034053, A034054, A034055, A034056 (numbers having multiplicative digital roots 0-9).
Sequence in context: A136192 A118431 A051809 * A120876 A216073 A086870
Adjacent sequences: A034051 A034052 A034053 * A034055 A034056 A034057
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KEYWORD
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nonn,base
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AUTHOR
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Patrick De Geest, Sep 15 1998.
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STATUS
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approved
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