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A072611
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Numbers n such that phi(n) divides sigma(n+1)-sigma(n).
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0
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| Conjecture : lim n -> infinity Log(a(n))/Log(n) exists = 2, 6.......
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MATHEMATICA
| Select[Range[20000], Divisible[DivisorSigma[1, #+1]-DivisorSigma[1, #], EulerPhi[#]]&] (* From Harvey P. Dale, Sep 15 2011 *)
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CROSSREFS
| Sequence in context: A112511 A063452 A009299 * A192966 A000918 A122958
Adjacent sequences: A072608 A072609 A072610 * A072612 A072613 A072614
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KEYWORD
| nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 07 2002
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