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%I #10 Sep 12 2013 12:49:44
%S 1,2,3,4,5,7,8,10,11,12,13,15,17,18,19,21,24,25,26,27,29,30,31,34,37,
%T 40,41,43,44,45,46,47,49,50,55,56,58,61,63,64,65,67,68,69,70,71,73,74,
%U 75,76,79,80,81,89,91,93,97,98,99,100,101,104,105,106,108
%N Denominators of rational numbers having continued fraction consisting entirely of 1s and 2s.
%C Related to Zaremba's conjecture. - _Charles R Greathouse IV_, Sep 12 2013
%H Vincenzo Librandi, <a href="/A228803/b228803.txt">Table of n, a(n) for n = 1..1000</a>
%e Rationals given by continued fractions as lexicographically ordered tuples of 1s and 2s: [1] = 1/1, [2] = 2/1, [1,1] = 2/1, [1,2] = 3/2, [2,1] = 3/1, [2,2] = 5/2, [1,1,1] = 3/2. The list continues: 5/3, 4/3, 7/5, 5/2, 8/3, 7/3, 12/5, 5/3, 8/5, 7/4, 12/7, 7/5, 11/8, 10/7, 17/12, 8/3, 13/5, 11/4, 19/7, 12/5, 19/8, 17/7, 29/12.
%t Sort[Union[Denominator[Map[FromContinuedFraction, Flatten[Map[Tuples[{1, 2}, #] &, Range[13]], 1]]]]]
%Y Cf. A228804, A228805.
%K nonn,easy
%O 1,2
%A _Clark Kimberling_, Sep 04 2013
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