%I A066945
%S A066945 11,11063,11943,38585,39995,43021,63349,67709,967393,1267511,2020925,
%T A066945 2915307,5805559,6584747,6659429,8064017,26260385,27681847,31886881,
%U A066945 41932769,48922307,61270145,71429011,89087903,91364345,191945623
%N A066945 Numbers n such that phi(phi(n)) + sigma(sigma(n)) - phi(sigma(n)) - sigma(phi(n)) 
               = phi(n).
%e A066945 Let n = 11. Then phi(phi(n)) + sigma(sigma(n)) - phi(sigma(n)) - sigma(phi(n)) 
               = phi(10) + sigma(12) - phi(12) - sigma(10) = 4 + 28 - 4 - 18 = 10 
               = phi(n), so 11 is in the sequence.
%t A066945 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==a]; Do[If[g[n]==True, Print[n]], {n, 1, 10^5}]
%Y A066945 Cf. A000010, A000203, A066850, A066939, A066946.
%Y A066945 Sequence in context: A138713 A068223 A068224 this_sequence A113615 A034873 
               A075854
%Y A066945 Adjacent sequences: A066942 A066943 A066944 this_sequence A066946 A066947 
               A066948
%K A066945 nonn
%O A066945 1,1
%A A066945 Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Jan 24 2002
%E A066945 Edited by Dean Hickerson (dean.hickerson(AT)yahoo.com), Jan 26 2002
%E A066945 a(17)-a(26) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Jan 
               02 2009