%I #15 Apr 18 2017 07:04:19
%S 1,0,4,2,18,18,86,122,430,746,2222,4346,11742,24682,62958,138202,
%T 340670,767562,1853838,4242746,10122974,23386282,55392686,128691866,
%U 303490046,707472138,1664048590,3886957050,9128207134,21347938154
%N Expansion of (1-x)/(1-x-4x^2+2x^3).
%H INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=1038">Encyclopedia of Combinatorial Structures 1038</a>
%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (1,4,-2)
%F G.f.: -(-1+x)/(1-x-4*x^2+2*x^3)
%F Recurrence: {a(1)=0, a(0)=1, a(2)=4, 2*a(n)-4*a(n+1)-a(n+2)+a(n+3)=0}
%F Sum(-1/79*(-1-36*_alpha+15*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(1-_Z-4*_Z^2+2*_Z^3))
%p spec := [S,{S=Sequence(Prod(Union(Prod(Sequence(Z),Z),Z),Union(Z,Z)))},unlabeled ]: seq(combstruct[count ](spec,size=n), n=0..20);
%K easy,nonn
%O 0,3
%A encyclopedia(AT)pommard.inria.fr, Jan 25 2000
%E More terms from _James A. Sellers_, Jun 06 2000