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A127105 Numbers n such that n^2 divides 5^n-1. +0
21
1, 2, 4, 6, 12, 42, 52, 84, 156, 186, 372, 1092, 1218, 1302, 1806, 2436, 2604, 2756, 3612, 4836, 5334, 7212, 8268, 10668, 12324, 15918, 18858, 24492, 31668, 31836, 33852, 37716, 37758, 46956, 50484, 52374, 55986, 57876, 71862, 75516, 86268 (list; graph; listen)
OFFSET

1,2

COMMENT

a(n) is a subset of A067946(n) = {1, 2, 4, 6, 8, 12, 16, 18, 24, 32, 36, 42, 48, 52, 54, 64, 72, 84, 96, ...} Numbers n such that n divides 5^n-1.

MATHEMATICA

Select[Range[30000], IntegerQ[(PowerMod[5, #, #^2 ]-1)/#^2 ]&]

CROSSREFS

Cf. A127100, A127101, A127102, A127103, A123104, A127106, A127107, A127092. Cf. A067946 = numbers n such that n divides 5^n-1.

Sequence in context: A143474 A087902 A081457 this_sequence A110980 A058598 A087549

Adjacent sequences: A127102 A127103 A127104 this_sequence A127106 A127107 A127108

KEYWORD

hard,nonn

AUTHOR

Alexander Adamchuk (alex(AT)kolmogorov.com), Jan 05 2007

EXTENSIONS

More terms from Ryan Propper (rpropper(AT)stanford.edu) and Alexander Adamchuk (alex(AT)kolmogorov.com), Jan 05 2007

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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