%I #10 Sep 01 2013 02:23:11
%S 1,27,405,25515,2066715,7577955,2659862205,71816279535,3662630256285,
%T 626309773824735,2415766270466835,166687872662211615,
%U 7500954269799522675,1822731887561284010025,52859224739277236290725
%N Denominators of partial sums of series for 3*arctanh(1/3) = (3/2)*log(2).
%C Numerators are given in A096949.
%F a(n)=denominator(A(n)) with the rational number A(n):= sum(((1/3)^(2*k))/(2*k+1), k=0..n) in lowest terms.
%e n=10: A096949(10)/2415766270466835 = 2511722368895123/2415766270466835 = 1.039720770838... approximates 3*arctanh(1/3)= 1.039720770840...
%K nonn,easy,frac
%O 0,2
%A _Wolfdieter Lang_, Jul 16 2004