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 A052708 #14 Jan 13 2025 09:20:23
%S A052708 0,0,1,2,5,16,56,204,768,2970,11726,47060,191412,787304,3269100,
%T A052708 13684864,57691353,244713654,1043684478,4472828400,19252045120,
%U A052708 83188965420,360734837280,1569296837160,6846931211250,29954007587556,131367797081352,577451514567536
%N A052708 A simple context-free grammar: convolution square of A049140.
%H A052708 INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=663">Encyclopedia of Combinatorial Structures 663</a>
%F A052708 G.f.: RootOf(-_Z+_Z^4+_Z^2+x)^2.
%F A052708 Recurrence: {a(1)=0, a(2)=1, a(3)=2, a(4)=5, (-576-1920*n+3072*n^2+6144*n^3)*a(n)+(-9096-30320*n-28032*n^2-7936*n^3)*a(n+1)+(41380*n+20808+28032*n^2+6272*n^3)*a(n+2)+(-26520*n^2-60704*n-45600-3784*n^3)*a(n+3)+(589*n^3+5301*n^2+15314*n+14136)*a(n+4)}.
%p A052708 spec := [S,{C=Prod(S,S),S=Prod(B,B),B=Union(S,C,Z)},unlabeled]: seq(combstruct[count](spec,size=n), n=0..20);
%Y A052708 Cf. A049140.
%K A052708 easy,nonn
%O A052708 0,4
%A A052708 encyclopedia(AT)pommard.inria.fr, Jan 25 2000