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 A052725 #13 Jun 03 2022 18:19:27
%S A052725 0,0,0,0,24,480,10080,262080,8104320,287400960,11496038400,
%T A052725 512691379200,25231888281600,1358412133478400,79419074570035200,
%U A052725 5011102330730496000,339416862385176576000,24564200609223475200000
%N A052725 A simple context-free grammar in a labeled universe.
%H A052725 INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=681">Encyclopedia of Combinatorial Structures 681</a>
%F A052725 E.g.f.: RootOf(-_Z+_Z^4+_Z^2+x)-RootOf(-_Z+_Z^4+_Z^2+x)^2-x
%F A052725 D-finite Recurrence: {a(1)=0, a(2)=0, a(3)=0, a(4)=24, a(5)=480, a(6)=10080, (-32256*n^3+85248*n^2-73728*n^5+2304*n-4608-184320*n^4)*a(n) +(-41472*n^3-241344*n^2-92736-289440*n+9216*n^4)*a(n+1) +(-59520*n^2-34048*n^3+79800+56512*n)*a(n+2) +(-7456*n^2-46176*n-61988)*a(n+3) +(-572+2228*n)*a(n+4) +217*a(n+5) =0.
%F A052725 a(n) = n!*A052710(n). - _R. J. Mathar_, Oct 18 2013
%p A052725 spec := [S,{B=Prod(C,C),C=Union(B,S,Z),S=Prod(B,B)},labeled]: seq(combstruct[count](spec,size=n), n=0..20);
%K A052725 easy,nonn
%O A052725 0,5
%A A052725 encyclopedia(AT)pommard.inria.fr, Jan 25 2000