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A074869 Numbers n such that sigma(sigma(n) - phi(n)) = phi(n). 0
707, 7843, 143591, 274211, 598787, 737807, 861749, 928421, 1515521, 1682203, 1936099, 2223143, 2709473, 2908373, 2985641, 3669919, 3689279, 3825419, 3848851, 4154297, 4429159, 5321743, 5654623, 5678131, 6548899, 8916427, 11403743, 11474267, 12191803, 13340869 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..30.

EXAMPLE

sigma(sigma(707)-phi(707)) = sigma(816-600) = sigma(216) = 600 = phi(707), so 707 is a term of the sequence.

MATHEMATICA

Select[Range[2, 10^6], DivisorSigma[1, DivisorSigma[1, # ] - EulerPhi[ # ]] == EulerPhi[ # ] &]

CROSSREFS

Sequence in context: A005845 A183795 A252692 * A212476 A188098 A306365

Adjacent sequences:  A074866 A074867 A074868 * A074870 A074871 A074872

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Sep 12 2002

EXTENSIONS

a(9)-a(30) from Donovan Johnson, Jan 19 2012

STATUS

approved

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Last modified June 17 14:09 EDT 2019. Contains 324185 sequences. (Running on oeis4.)