Search: id:A066946
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%I A066946
%S A066946 827,975,1607,13149,20919,34921,58649,202223,347869,545377,900521,
%T A066946 1451135,2288845,2453509,2804855,3063031,4134579,11320177,11446955,
%U A066946 14573651,16477307,17678225,25164429,27514643,28475077,47443799
%N A066946 Numbers n such that phi(phi(n)) + sigma(sigma(n)) - phi(sigma(n)) - sigma(phi(n)) 
               = sigma(n).
%e A066946 Let n = 827. Then phi(phi(n)) + sigma(sigma(n)) - phi(sigma(n)) - sigma(phi(n)) 
               = phi(826) + sigma(828) - phi(828) - sigma(826) = 348 + 2184 - 264 
               - 1440 = 828 = sigma(n), so 827 is in the sequence.
%t A066946 g[x_] := Module[{a, b, c, d, e, f}, a=EulerPhi[x]; b=DivisorSigma[1, 
               x]; c=EulerPhi[a]; d=DivisorSigma[1, b]; e=EulerPhi[b]; f=DivisorSigma[1, 
               a]; c+d-e-f==b]; Do[If[g[n]==True, Print[n]], {n, 1, 10^5}]
%Y A066946 Cf. A000010, A000203, A066850, A066939, A066945.
%Y A066946 Sequence in context: A057002 A051989 A104375 this_sequence A143799 A046496 
               A102350
%Y A066946 Adjacent sequences: A066943 A066944 A066945 this_sequence A066947 A066948 
               A066949
%K A066946 nonn
%O A066946 1,1
%A A066946 Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Jan 24 2002
%E A066946 Edited by Dean Hickerson (dean.hickerson(AT)yahoo.com) and Robert G. 
               Wilson v (rgwv(AT)rgwv.com), Jan 26 2002
%E A066946 a(23)-a(26) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Jan 
               02 2009

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