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Search: id:A065875
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| A065875 |
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Usigma(Phi(n)) is a prime. |
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+0
2
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| 3, 4, 5, 6, 8, 10, 12, 17, 32, 34, 40, 48, 60, 257, 512, 514, 544, 640, 680, 768, 816, 960, 1020, 65537, 131072, 131074, 131584, 139264, 139808, 163840, 164480, 174080, 174760, 196608, 197376, 208896, 209712, 245760, 246720, 261120, 262140
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OFFSET
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1,1
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COMMENT
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n is odd for only 3, 5, 17, 257 & 65537 for n < 10^7; they being the Fermat primes.
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MATHEMATICA
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f[n_] := Block[ {a = FactorInteger[n], k = l = s = 1}, l = Length[a]; While[k <= l, s = s * (a[[k, 1]]^a[[k, 2]] + 1); k++ ]; Return[s]]; Select[ Range[10^7], PrimeQ[ f[ EulerPhi[ # ]]] & ]
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CROSSREFS
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Cf. A062514.
Sequence in context: A120162 A002859 A062514 this_sequence A100585 A023367 A047426
Adjacent sequences: A065872 A065873 A065874 this_sequence A065876 A065877 A065878
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KEYWORD
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nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 07 2001
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