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A066155
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Numbers k such that EulerPhi(k) = sigma(k+1) - sigma(k-1).
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1
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4, 6, 11, 32, 38, 54, 84, 278, 407, 804, 1854, 2664, 3287, 6579, 11327, 14750, 15608, 20720, 41664, 46839, 70190, 73283, 80429, 185231, 241614, 275876, 355292, 375200, 410327, 511220, 692909, 763179, 901494, 920390, 1089984, 1099196, 1356759
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OFFSET
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1,1
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LINKS
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EXAMPLE
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EulerPhi(6) = 2 = 8 - 6 = sigma(7) - sigma(5).
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MATHEMATICA
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Select [Range[1, 10^6], EulerPhi[ # ] == DivisorSigma[1, # + 1] - DivisorSigma[1, # - 1] & ]
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PROG
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(PARI) { n=0; for (m=2, 10^9, if (eulerphi(m) == sigma(m + 1) - sigma(m - 1), write("b066155.txt", n++, " ", m); if (n==100, return)) ) } \\ Harry J. Smith, Feb 03 2010
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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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