%I A068563
%S A068563 1,2,4,6,8,12,16,18,20,24,32,36,40,42,48,54,60,64,72,80,84,96,100,108,
%T A068563 120,126,128,136,144,156,160,162,168,180,192,200,216,220,240,252,256,
%U A068563 272,288,294,300,312,320,324,336,342,360,378,384,400,408,420,432,440
%N A068563 Numbers n such that 2^n (mod n) = 4^n (mod n).
%C A068563 If k is in the sequence then 2k is also in the sequence, but the converse 
               is not true.
%C A068563 Almost the same as A124240, numbers n such that lambda(n) divides n, 
               where lambda(n) is Carmichael's lambda function, A002322. - T. D. 
               Noe (noe(AT)sspectra.com), May 30 2003
%H A068563 T. D. Noe, <a href="b068563.txt">Table of n, a(n) for n = 1..1000</a>
%H A068563 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               CarmichaelFunction.html">Carmichael Function</a>
%t A068563 Select[Range[500], PowerMod[2,#,# ] == PowerMod[4,#,# ] & ]
%Y A068563 Cf. A002322.
%Y A068563 Sequence in context: A125225 A092903 A005153 this_sequence A124240 A068997 
               A067712
%Y A068563 Adjacent sequences: A068560 A068561 A068562 this_sequence A068564 A068565 
               A068566
%K A068563 easy,nonn
%O A068563 1,2
%A A068563 Benoit Cloitre (benoit7848c(AT)orange.fr), Mar 25 2002
%E A068563 Comment and Mathematica program corrected by T. D. Noe (noe(AT)sspectra.com), 
               Oct 17 2008