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A052668 E.g.f. 1/(1-3x-x^3). 0

%I

%S 1,3,18,168,2088,32400,603360,13109040,325503360,9092684160,

%T 282219033600,9635476435200,358879494758400,14480588157235200,

%U 629228583138355200,29295027261916416000,1454816084780298240000

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

%H INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=616">Encyclopedia of Combinatorial Structures 616</a>

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

%F Recurrence: {a(0)=1, a(1)=3, a(2)=18, (-11*n-6-n^3-6*n^2)*a(n)+(-3*n-9)*a(n+2)+a(n+3)=0}

%F Sum(1/15*(4+_alpha+2*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(-1+3*_Z+_Z^3))*n!.

%F a(n)=n!*A052541(n). - _R. J. Mathar_, Nov 27 2011

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

%K easy,nonn

%O 0,2

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

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Last modified July 5 19:02 EDT 2020. Contains 335473 sequences. (Running on oeis4.)