%I
%S 1,2,3,4,5,7,8,11,13,16,17,19,23,28,29,31,32,37,41,43,47,53,59,61,64,
%T 67,71,73,79,83,89,97,101,103,107,109,112,113,127,128,131,137,139,149,
%U 151,157,163,167
%N Numbers n such that (2^(n1) mod n)=(4^(n1) mod n).
%C Numbers n such that A062173(n)=A062175(n).
%C Question: is the sequence (Powers of 2) UNION (odd primes), the union of A000079 and A005408?
%C The answer to the question is No: 2^(281) mod 28 = 4^(281) mod 28 = 8. Also, any base2 Fermat pseudoprime (A001567) is a member of this sequence.  _D. S. McNeil_, Dec 07 2010
%H Harvey P. Dale, <a href="/A176176/b176176.txt">Table of n, a(n) for n = 1..10000</a>
%t Select[Range[200],PowerMod[2,#1,#]==PowerMod[4,#1,#]&] (* _Harvey P. Dale_, Nov 10 2011 *)
%Y Cf. A000079, A005408, A062173.
%K nonn
%O 1,2
%A _JuriStepan Gerasimov_, Dec 07 2010
%E Extended by _D. S. McNeil_, Dec 07 2010
