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 A085571 #4 Mar 30 2012 16:49:45 %S A085571 2,6,11,20,101,175,593,173,1502,2684,28649,52169,662393,1224077, %T A085571 4506259,4210067,23506871,44294491,41572193,78849257,1639049932, %U A085571 3125022742,23750582143,9095291663,225666905951,144544431373,276913262539,76244134117,732674442397 %N A085571 Numerator 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 A085571 2, 6, 11, 20, 101/3, 175/3, 593/6, 173, 1502/5, 2684/5, 28649/30, ... %p A085571 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 A085571 Cf. A085568-A086673. %K A085571 nonn,frac %O A085571 2,1 %A A085571 _N. J. A. Sloane_, Jul 07 2003