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A074869 Numbers n such that sigma(sigma(n) - phi(n)) = phi(n). 0

%I

%S 707,7843,143591,274211,598787,737807,861749,928421,1515521,1682203,

%T 1936099,2223143,2709473,2908373,2985641,3669919,3689279,3825419,

%U 3848851,4154297,4429159,5321743,5654623,5678131,6548899,8916427,11403743,11474267,12191803,13340869

%N Numbers n such that sigma(sigma(n) - phi(n)) = phi(n).

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

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

%K nonn

%O 1,1

%A _Joseph L. Pe_, Sep 12 2002

%E a(9)-a(30) from _Donovan Johnson_, Jan 19 2012

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Last modified September 17 17:29 EDT 2014. Contains 246866 sequences.