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Search: id:A127102
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| A127102 |
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Numbers n such that n^2 divides 8^n-1. |
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24
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| 1, 7, 889, 2359, 299593, 2033143, 13549249, 42931441, 100170217, 310935751, 685169191
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OFFSET
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1,2
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COMMENT
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a(n) is a subset of A014949(n) = {1, 7, 49, 343, 889, 2359, 2401, 6223, 16513, ...} Numbers n such that n divides 8^n-1.
a(5) = 299593 = (8^7-1)/7 is a repunit in base 8, 1111111( base 8). Note that the first 5 listed terms of a(n) are the terms of a finite sequence {1, 7, 49, 127, 337, 889, 2359, 6223, 16513, 42799, 299593, 2097151} = A003530(n) Divisors of 2^21 - 1.
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MATHEMATICA
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Select[Range[20000], IntegerQ[(PowerMod[8, #, #^2 ]-1)/#^2 ]&]
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CROSSREFS
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Cf. A127100, A127101, A127103, A127104, A127105, A127106, A127107, A127092. Cf. A014949 = numbers n such that n divides 8^n-1.
Cf. A003530.
Sequence in context: A047788 A087350 A093171 this_sequence A038808 A068728 A028990
Adjacent sequences: A127099 A127100 A127101 this_sequence A127103 A127104 A127105
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KEYWORD
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hard,more,nonn
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AUTHOR
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Alexander Adamchuk (alex(AT)kolmogorov.com), Jan 05 2007, Jan 07 2007
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EXTENSIONS
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More terms from Ryan Propper (rpropper(AT)stanford.edu), Jan 05 2007
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