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A072611
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Numbers k such that phi(k) divides sigma(k+1) - sigma(k).
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1
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1, 2, 6, 14, 30, 40, 70, 140, 170, 174, 206, 215, 238, 390, 459, 518, 923, 957, 1334, 1364, 1540, 1634, 2685, 2974, 4364, 5180, 5934, 6048, 6467, 6510, 6623, 8028, 8094, 8260, 8814, 12136, 12954, 14099, 14841, 15416, 16472, 17094, 17835, 17927, 18873
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OFFSET
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1,2
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LINKS
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FORMULA
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Conjecture : Limit_{n -> infinity} log(a(n))/log(n) exists and = 2.6... .
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MATHEMATICA
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Select[Range[20000], Divisible[DivisorSigma[1, #+1]-DivisorSigma[1, #], EulerPhi[#]]&] (* Harvey P. Dale, Sep 15 2011 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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