This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A085572 #5 Mar 30 2012 16:49:45 %S A085572 1,1,1,1,3,3,6,1,5,5,30,30,210,210,420,210,630,630,315,315,3465,3465, %T A085572 13860,2772,36036,12012,12012,1716,8580,8580,17160,8580,145860,204204, %U A085572 612612,612612,11639628,11639628,29099070,29099070,29099070,29099070,1322685,14549535 %N A085572 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 A085572 2, 6, 11, 20, 101/3, 175/3, 593/6, 173, 1502/5, 2684/5, 28649/30, ... %p A085572 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 A085572 Cf. A085568-A086673. %K A085572 nonn,frac %O A085572 2,5 %A A085572 _N. J. A. Sloane_, Jul 07 2003