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A052669 E.g.f. (1-2x)/(1-3x-x^2+2x^3). 0

%I

%S 1,1,8,66,840,12960,242640,5286960,131765760,3693755520,115058361600,

%T 3942342835200,147360531225600,5967185903078400,260221271108198400,

%U 12158477739023616000,605960547270414336000,32087688283562655744000

%N E.g.f. (1-2x)/(1-3x-x^2+2x^3).

%H INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=617">Encyclopedia of Combinatorial Structures 617</a>

%F E.g.f.: -(-1+2*x)/(1-3*x-x^2+2*x^3)

%F Recurrence: {a(1)=1, a(0)=1, a(2)=8, (12+2*n^3+12*n^2+22*n)*a(n)+(-n^2-5*n-6)*a(n+1)+(-3*n-9)*a(n+2)+a(n+3)=0}

%F Sum(-1/229*(-5-74*_alpha+16*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(1-3*_Z-_Z^2+2*_Z^3))*n!

%F a(n) = n!*A052550(n). - _R. J. Mathar_, Nov 27 2011

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

%K easy,nonn

%O 0,3

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

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Last modified August 15 16:02 EDT 2020. Contains 336505 sequences. (Running on oeis4.)