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 A107704 #3 Mar 30 2012 18:59:07
%S A107704 1,1,2,3,8,26,107,492,2481,13599,81288,531343,3790344,29279668,
%T A107704 242278645,2125160800,19608039385,189437263949,1912477987102,
%U A107704 20161911603747,221869317899264,2546362514225134,30430660439311103
%N A107704 Diagonal sums of A103209, viewed as number triangle.
%F A107704 a(n)=sum{k=0..floor(n/2), sum{j=0..n-2k, C(n-2k+j, 2j)*k^j*C(k)}}, C(n) given by A000108.
%K A107704 easy,nonn
%O A107704 0,3
%A A107704 _Paul Barry_, May 21 2005