%I #17 Jul 15 2017 11:22:32
%S 2,2,2,2,10,90,4410,2033010,47753371890,536047310324601810,
%T 146146505822254040921594435610,
%U 461461505298297622704608601547181743257756610890,409066116871912908631970281597531260628466742447938742767153852110729821286410
%N The denominator of r(n), where r(n) = 1/r(n-2) + r(n-1); r(1)=r(2)=1/2.
%C It appears that the sequence is always in simplest terms when generated.
%t r[n_] := r[n] = If[n <= 2, 1/2, 1/r[n - 2] + r[n - 1]]; Denominator@ Array[r, 13] (* _Michael De Vlieger_, Jul 15 2017 *)
%Y Cf. A289909 (numerators).
%K nonn,frac
%O 1,1
%A _John Harmon_, Jul 15 2017