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%I #20 Sep 08 2022 08:45:23
%S 1,170,595,714,121056,480441,529620,706063,706237,729752,755972,
%T 815654,2162808,2449062,2827789,2927848,2957416,2994681,2995419,
%U 3010227,3019028,3019772,3080140,3093860,3103464,3206364,3213804
%N Numbers k such that phi(k)*sigma(k) is a fourth power.
%D J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 170, p. 54, Ellipses, Paris 2008.
%H Amiram Eldar, <a href="/A114078/b114078.txt">Table of n, a(n) for n = 1..600</a>
%e phi(595) * sigma(595) = 331776 = 24^4.
%t Select[Range[3300000],IntegerQ[Power[EulerPhi[#] DivisorSigma[1,#], (4)^-1]]&] (* _Harvey P. Dale_, Mar 14 2011 *)
%o (PARI) isok(n) = ispower(eulerphi(n)*sigma(n), 4); \\ _Michel Marcus_, Jan 09 2014
%o (Magma) [k:k in [1..3300000]| IsPower(EulerPhi(k)*DivisorSigma(1,k),4)]; // _Marius A. Burtea_, Sep 19 2019
%Y Cf. A062354, subsequence of A011257.
%K nonn
%O 1,2
%A _Giovanni Resta_, Feb 13 2006
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