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%I #8 Dec 29 2013 22:03:12
%S 1,2,3,4,5,6,7,8,9,11,12,13,16,17,18,19,21,23,24,25,27,28,29,31,32,36,
%T 37,41,43,47,48,49,53,54,59,61,64,67,71,72,73,79,81,83,89,96,97,101,
%U 103,107,108,109,112,113,121,125,127,128,131,137,139,144,149,151,157
%N Numbers n for which n is congruent to n^2 mod phi(n).
%C Or, numbers n such that phi(n) divides n*(n-1). - Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), Apr 14 2006
%H Charles R Greathouse IV, <a href="/A072303/b072303.txt">Table of n, a(n) for n = 1..10000</a>
%e 9 is in the sequence because phi(9) = 6. 9 % 6 = 3 and 9^2 % 6 = 3. But 10 is not in the sequence because phi(10) = 4 and 10 % 4 = 6 and 10^2 % 4 = 0.
%o (PARI) isok(n) = ((n^2 - n) % eulerphi(n)) == 0 \\ _Michel Marcus_, Jun 07 2013
%Y Cf. A000010, A068494.
%K easy,nonn
%O 1,2
%A Igor Naverniouk (igor(AT)lexansoft.com), Jul 14 2002
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