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Numbers k such that 2^k mod phi(k) = 2^phi(k) mod k.
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%I #12 Feb 11 2021 01:27:09

%S 1,2,4,8,16,32,64,108,128,188,224,252,256,288,296,336,448,504,512,576,

%T 672,716,972,1008,1024,1404,1472,2016,2048,2268,2808,3324,3888,4096,

%U 4860,5184,5500,6480,7776,8192,8748,8952,9720,9896,11000,11104,12256

%N Numbers k such that 2^k mod phi(k) = 2^phi(k) mod k.

%H Harvey P. Dale, <a href="/A069050/b069050.txt">Table of n, a(n) for n = 1..300</a>

%t Select[Range[13000],PowerMod[2,#,EulerPhi[#]]==PowerMod[2, EulerPhi[ #],#]&] (* _Harvey P. Dale_, Aug 21 2016 *)

%K easy,nonn

%O 1,2

%A _Benoit Cloitre_, Apr 03 2002