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%I #22 Aug 06 2020 22:46:02
%S 3597,3955,5635,1388763,3155577,6718173,10541751,11333043,12331467,
%T 15477033,18454809,19062465,21229131,25243618,32750823,38975607,
%U 41126645,42756555,45016767,48072753,73061703,81409317,84235965,87999021,93936513,106749513,128812167
%N Numbers n such that sigma(phi(n)) = sigma(n) + phi(n).
%H Donovan Johnson, <a href="/A230023/b230023.txt">Table of n, a(n) for n = 1..187</a> (terms < 3*10^10)
%e phi(3597)=2160, sigma(3597)=5280, sigma(2160)=7440 so sigma(phi(3597))=7440=5280+2160=sigma(3597)+phi(3597) and 3597 is in the sequence.
%t Do[If[DivisorSigma[1,EulerPhi[n]] == DivisorSigma[1,n] + EulerPhi[n], Print[n]], {n, 200000000}]
%t spQ[n_]:=Module[{phi=EulerPhi[n]},DivisorSigma[1,phi]==DivisorSigma[ 1,n]+ phi]; Select[Range[129*10^6],spQ] (* _Harvey P. Dale_, Aug 06 2020 *)
%Y Cf. A000010, A000203, A062402.
%K nonn
%O 1,1
%A _Farideh Firoozbakht_, Oct 16 2013
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