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 A052625 #15 Jun 03 2022 18:37:25
%S A052625 1,0,0,6,48,360,3600,45360,645120,10160640,177811200,3432844800,
%T A052625 72329241600,1650160512000,40537905408000,1067062284288000,
%U A052625 29961435119616000,893842506805248000,28234468042260480000
%N A052625 E.g.f. (1-x)^2/(1-2x+x^2-x^3).
%H A052625 INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=571">Encyclopedia of Combinatorial Structures 571</a>
%F A052625 E.g.f.: -(-1+x)^2/(-1+2*x-x^2+x^3)
%F A052625 Recurrence: {a(1)=0, a(0)=1, a(2)=0, (-11*n-6-n^3-6*n^2)*a(n) +(n^2+5*n+6)*a(n+1) +(-2*n-6)*a(n+2) +a(n+3)=0}
%F A052625 Sum(-1/23*(2-11*_alpha+6*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(-1+2*_Z-_Z^2+_Z^3))*n!
%F A052625 a(n) = (-1)^n*n!*A099529(n). - _R. J. Mathar_, Jun 03 2022
%p A052625 spec := [S,{S=Sequence(Prod(Z,Z,Z,Sequence(Z),Sequence(Z)))},labeled]: seq(combstruct[count](spec,size=n), n=0..20);
%t A052625 With[{nn=20},CoefficientList[Series[(1-x)^2/(1-2x+x^2-x^3),{x,0,nn}], x]Range[0,nn]!] (* _Harvey P. Dale_, May 22 2012 *)
%K A052625 easy,nonn
%O A052625 0,4
%A A052625 encyclopedia(AT)pommard.inria.fr, Jan 25 2000