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 A158829 #2 Mar 30 2012 18:37:16
%S A158829 1,1,2,5,15,52,202,861,3972,19648,103500,577443,3396804,20988116,
%T A158829 135770140,916936351,6449233093,47137434787,357331341987,
%U A158829 2804582808108,22754919576652,190578011064394,1645490708244886,14629351150837605
%N A158829 Antidiagonal sums of square array A158825, in which row n lists the coefficients of the n-th iteration of x*C(x), where C(x) is the Catalan function (A000108).
%o A158829 (PARI) {a(n)=local(F=serreverse(x-x^2+O(x^(n+1))),G=x,ADS=0); for(k=1,n,G=x;for(i=1,n-k,G=subst(F,x,G));ADS=ADS+polcoeff(G,k));ADS}
%Y A158829 Cf. A158825, A158826, A158827, A158828.
%K A158829 nonn
%O A158829 1,3
%A A158829 _Paul D. Hanna_, Mar 28 2009