This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

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