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A055681
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Numbers k that divide sigma(k)-phi(k).
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3
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1, 2, 12, 42, 1242, 75960, 1447488, 3506976, 6137440, 10834488, 17156160, 90288000, 431440416, 454460160, 704592000, 1385119360, 1588268480, 10674673152, 24913095480, 31103703540, 56015374080, 80767843200, 129631788000, 463308768000, 469897798656, 834460413696
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OFFSET
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1,2
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COMMENTS
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LINKS
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MAPLE
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MATHEMATICA
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Do[If[Mod[DivisorSigma[1, n]-EulerPhi[n], n]==0, Print[n]], {n, 1, 10^9}]
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PROG
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(PARI)
for(n=1, 10^8, if((sigma(n)-eulerphi(n))%n==0, print1(n, ", "))) \\ Derek Orr, Sep 13 2014
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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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