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 A052970 #16 Jul 02 2025 16:01:58
%S A052970 1,0,2,2,8,16,44,104,264,648,1616,4000,9936,24640,61152,151712,376448,
%T A052970 934016,2317504,5750144,14267264,35399808,87833856,217932800,
%U A052970 540733696,1341665280,3328932352,8259727872,20493989888,50849570816,126167665664
%N A052970 Expansion of (1-2x)/(1-2x-2x^2+2x^3).
%H A052970 INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=1042">Encyclopedia of Combinatorial Structures 1042</a>
%H A052970 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (2,2,-2).
%F A052970 G.f.: -(-1+2*x)/(1-2*x-2*x^2+2*x^3)
%F A052970 Recurrence: {a(1)=0, a(0)=1, a(2)=2, 2*a(n)-2*a(n+1)-2*a(n+2)+a(n+3)}
%F A052970 Sum(-1/37*(3-15*_alpha+2*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(2*_Z^3-2*_Z^2-2*_Z+1))
%p A052970 spec := [S,{S=Sequence(Prod(Union(Prod(Sequence(Union(Z,Z)),Z),Z),Z))},unlabeled ]: seq(combstruct[count ](spec,size=n), n=0..20);
%K A052970 easy,nonn
%O A052970 0,3
%A A052970 encyclopedia(AT)pommard.inria.fr, Jan 25 2000
%E A052970 More terms from _James Sellers_, Jun 05 2000