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A177012
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Numbers k such that k^k == -1 (mod phi(k)).
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1
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1, 2, 3, 15, 87, 255, 11759, 26279, 39455, 43919, 65535, 112895, 443807, 1347455, 1464911, 1568255, 1604559, 1968095, 2441559, 5948799, 16210655, 39624767, 39839039, 59187455, 81624279, 83623935, 251009695, 256685439, 338979839, 434357967, 455345855, 471783935, 487722815, 518291135, 596835839
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OFFSET
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1,2
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COMMENTS
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3 is the largest prime term of this sequence.
All terms are squarefree. There is no further term up to 2*10^8.
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LINKS
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EXAMPLE
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phi(15)=8 and 15^15 == -1 (mod 8), so 15 is in the sequence.
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MATHEMATICA
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v={}; Do[If[PowerMod[n, n, EulerPhi[n]]==EulerPhi[n]-1, AppendTo[v, n];
Print[v]], {n, 200000000}]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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