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 A183203 #10 Mar 29 2025 18:16:11
%S A183203 1,1,3,4,9,14,31,53,117,215,478,930,2092,4266,9732,20645,47820,104941,
%T A183203 246931,558190,1334462,3097018,7521731,17874931,44092014
%N A183203 Antidiagonal sums of triangle A183202.
%o A183203 (PARI) {A131338(n, k)=if(k>n*(n+1)/2||k<0,0,if(k<=n,1,sum(i=0, k-n,A131338(n-1,i))))}
%o A183203 {A183202(n,k)=if(n==k,A131338(n,n*(n+1)/2),sum(j=n*k-k*(k-1)/2,n*k-k*(k-1)/2+n-k-1,A131338(n,j)))}
%o A183203 {a(n)=sum(k=0,n,A183202(n-k,k))}
%Y A183203 Cf. A183202.
%K A183203 more,nonn
%O A183203 0,3
%A A183203 _Paul D. Hanna_, Dec 30 2010