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 A118929 #7 Mar 30 2012 18:36:57
%S A118929 1,1,2,5,14,44,152,569,2270,9524,41576,187432,868144,4117216,19945408,
%T A118929 98523013,495521686,2534420852,13167361256,69417635240,370991119792,
%U A118929 2008036459744,10997771773888,60896581502800,340633178891872
%N A118929 a(n) = Sum_{k=0..[n/2]} 2^(n-2*k-1)*C(n-1,2*k)*C(2*k,k)/(k+1)*a(k), with a(0)=1.
%C A118929 Invariant column vector V under matrix product A091894*V = V: a(n) = Sum_{k=0,[n/2]} A091894(n,k)*a(k), where A091894(n,k) = number of Dyck paths of semilength n, having k ddu's [here u=(1,1) and d=(1,-1)].
%o A118929 (PARI) {a(n)=if(n==0,1,sum(k=0,n\2,2^(n-2*k-1)*binomial(n-1,2*k)*binomial(2*k,k)/(k+1)*a(k)))}
%Y A118929 Cf. A091894.
%K A118929 nonn
%O A118929 0,3
%A A118929 _Paul D. Hanna_, May 06 2006