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 A085570 #4 Mar 30 2012 16:49:45 %S A085570 1,2,2,4,5,8,14,24,39,74,128,232,423,776,1426,2660,4931,9268,17346, %T A085570 32840,61903,117832,223410,427156,813812,1561830,2987535,5751742, %U A085570 11039759,21312036,41025866,79386066,153208323,297072312,574604611,1116186954,2163216427 %N A085570 If n mod 2 = 0 then 2*Sum(floor(C(n,w)/(2*w+1)),w=0..n/2-1)+floor(C(n,n/2)/(n+1)) otherwise 2*Sum(floor(C(n,w)/(2*w+1)),w=0..(n-1)/2). %p A085570 b := binomial; f2 := n->if n mod 2 = 0 then 2*add(floor(b(n,w)/(2*w+1)),w=0..n/2-1)+floor(b(n,n/2)/(n+1)); else 2*add(floor(b(n,w)/(2*w+1)),w=0..(n-1)/2); fi; %Y A085570 Cf. A085568-A086673. %K A085570 nonn %O A085570 0,2 %A A085570 _N. J. A. Sloane_, Jul 07 2003