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%I #15 Jul 31 2019 23:17:16
%S 12,48,56,80,192,240,252,351,448,768,992,1100,1134,1260,1280,1824,
%T 1872,2016,3072,3300,3520,3584,3840,3875,4352,5103,6156,9072,9120,
%U 9288,9477,9984,10962,11132,11264,12288,13056,16128,16256,20480,20592,21760,22736
%N Non-cyclic numbers n such that phi(n)^phi(n) == gcd(n, phi(n)) (mod n), where phi is Euler totient function.
%C The cyclic numbers satisfy phi(n)^phi(n) == gcd(n, phi(n))== 1 (mod n).
%H Charles R Greathouse IV, <a href="/A230919/b230919.txt">Table of n, a(n) for n = 1..3238</a>
%t Select[Range[40000], PowerMod[EulerPhi[#], EulerPhi[#], #] > 1 && PowerMod[EulerPhi[#], EulerPhi[#], #] == GCD[#, EulerPhi[#]] &]
%o (PARI) is(n)=my(p=eulerphi(n),g=gcd(p,n)); g>1 && Mod(p,n)^p==g \\ _Charles R Greathouse IV_, Dec 27 2013
%Y Cf. A003277, A230918.
%K nonn
%O 1,1
%A _José María Grau Ribas_, Nov 01 2013
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