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A127101
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Numbers n such that n^2 divides 9^n-1.
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25
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1, 2, 4, 8, 10, 20, 40, 110, 136, 164, 220, 328, 440, 610, 680, 820, 1210, 1220, 1544, 1640, 2420, 2440, 2530, 4840, 5060, 5576, 6710, 7370, 7480, 7720, 9020, 10120, 11810, 13420, 13612, 14008, 14740, 18040, 18632, 19580
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| a(n) is a subset of A068382(n) = {1, 2, 4, 8, 10, 16, 20, 32, 40, 50, 64, 80, 100, 110, 128, 136, 160, 164, 200, ...} Numbers n such that n divides 9^n-1.
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MATHEMATICA
| Select[Range[20000], IntegerQ[(PowerMod[9, #, #^2 ]-1)/#^2 ]&]
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CROSSREFS
| Cf. A127100, A127102, A127103, A123104, A127105, A127106, A127107, A127092. Cf. A068382 = numbers n such that n divides 9^n-1.
Sequence in context: A033092 A177909 A004655 * A124849 A056654 A020950
Adjacent sequences: A127098 A127099 A127100 * A127102 A127103 A127104
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KEYWORD
| nonn
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AUTHOR
| Alexander Adamchuk (alex(AT)kolmogorov.com), Jan 05 2007
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