%I #5 Mar 30 2012 16:49:45
%S 1,1,1,1,3,3,6,1,5,5,30,30,210,210,420,210,630,630,315,315,3465,3465,
%T 13860,2772,36036,12012,12012,1716,8580,8580,17160,8580,145860,204204,
%U 612612,612612,11639628,11639628,29099070,29099070,29099070,29099070,1322685,14549535
%N Denominator of 2*Sum(C(n,w)/w,w=1..n/2-1)+C(n, n/2)/(n/2) if n is even otherwise of 2*Sum(C(n,w)/w,w=1..(n-1)/2).
%e 2, 6, 11, 20, 101/3, 175/3, 593/6, 173, 1502/5, 2684/5, 28649/30, ...
%p b := binomial; f3 := n->if n mod 2 = 0 then 2*add(b(n,w)/w,w=1..n/2-1)+b(n, n/2)/(n/2); else 2*add(b(n,w)/w,w=1..(n-1)/2); fi;
%Y Cf. A085568-A086673.
%K nonn,frac
%O 2,5
%A _N. J. A. Sloane_, Jul 07 2003