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%I #12 Mar 17 2020 15:14:07
%S 1,4,13,20,24,36,40,65,64,84,112,96,128,121,171,186,200,216,168,208,
%T 192,273,312,340,392,364,480,448,456,496,612,605,576,640,768,768,840,
%U 880,840,936,960,1105,992,1200,1093,1280,1464,1364,1152,1539,1152,1664,1482
%N Integer of the form phi(n)*sigma(n)/n.
%H Harry J. Smith, <a href="/A066993/b066993.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = sigma(A011775(n))*phi(A011775(n))/A011775(n).
%t Select[Table[EulerPhi[n] DivisorSigma[1,n]/n,{n,2000}],IntegerQ] (* _Harvey P. Dale_, Mar 17 2020 *)
%o (PARI) { n=0; for (m=1, 10^10, if ((a=eulerphi(m)*sigma(m)/m) % 1.0 == 0 , write("b066993.txt", n++, " ", a); if (n==1000, return)) ) } \\ _Harry J. Smith_, Apr 16 2010
%Y Cf. A011775.
%K nonn
%O 1,2
%A _Benoit Cloitre_, Jan 27 2002
%E Missing term a(43)=992 and new term a(53)=1482 added by _Harry J. Smith_, Apr 16 2010
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