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A052583 E.g.f. x(1-x)/(1-x-x^2). 0

%I

%S 0,1,0,6,24,240,2160,25200,322560,4717440,76204800,1357171200,

%T 26345088000,554204851200,12553673932800,304688127744000,

%U 7887891787776000,216969331138560000,6319142847553536000

%N E.g.f. x(1-x)/(1-x-x^2).

%H INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=527">Encyclopedia of Combinatorial Structures 527</a>

%F E.g.f.: x*(-1+x)/(-1+x+x^2)

%F Recurrence: {a(1)=1, a(0)=0, a(2)=0, (-2-n^2-3*n)*a(n)+(-2-n)*a(n+1)+a(n+2)=0}

%F Sum(-1/5*(-3+4*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z+_Z^2))*n!

%p spec := [S,{S=Prod(Z,Sequence(Prod(Z,Z,Sequence(Z))))},labeled]: seq(combstruct[count](spec,size=n), n=0..20);

%t With[{nn=20},CoefficientList[Series[x (1-x)/(1-x-x^2),{x,0,nn}], x]Range[0,nn]!] (* _Harvey P. Dale_, Jul 24 2012 *)

%K easy,nonn

%O 0,4

%A encyclopedia(AT)pommard.inria.fr, Jan 25 2000

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Last modified June 16 19:49 EDT 2021. Contains 345068 sequences. (Running on oeis4.)