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 A136631 #2 Mar 30 2012 18:37:09
%S A136631 1,1,2,6,28,177,1449,14869,185230,2738962,47287352,939759621,
%T A136631 21241309681,540698975061,15370957337418,484433735633218,
%U A136631 16817886069720724,639545680226171989,26507567678760284105
%N A136631 Antidiagonal sums of triangle A136630, omitting antidiagonals of all zeros.
%F A136631 a(n) = Sum_{k=0..n} [x^(2n-2k)] Product_{j=0..[k/2]} 1/(1 - (2j + k-2[k/2])^2*x^2).
%o A136631 (PARI) {a(n)=sum(k=0,n,polcoeff(1/prod(j=0,k\2,1-(2*j+(k%2))^2*x^2 +x*O(x^(2*n-2*k))),2*n-2*k))}
%Y A136631 Cf. A136630, A003724 (row sums of A136630).
%K A136631 nonn
%O A136631 0,3
%A A136631 _Paul D. Hanna_, Jan 14 2008