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%I #13 Oct 15 2020 15:51:58
%S 2,6,8,9,24,28,70,78,128,140,222,234,280,312,350,366,384,438,496,525,
%T 666,864,888,910,918,936,942,1036,1098,1158,1232,1314,1400,1464,1575,
%U 1662,1708,1752,1824,1836,1878,1900,1938,2044,2382,2480,2526,2590,2664
%N Numbers n such that phi(sigma(n)) = 2*phi(n).
%H M. F. Hasler and Charles R Greathouse IV, <a href="/A067704/b067704.txt">Table of n, a(n) for n = 1..10000</a> (first 110 terms from Hasler)
%t Select[Range[3000],EulerPhi[DivisorSigma[1,#]]==2EulerPhi[#]&] (* _Harvey P. Dale_, Oct 15 2020 *)
%o (PARI) is(n)=2*eulerphi(n=factor(n))==eulerphi(sigma(n)) \\ _Charles R Greathouse IV_, Nov 27 2013
%Y Cf. A137815, A137816.
%K nonn
%O 1,1
%A _Benoit Cloitre_, Feb 05 2002
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