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A052744 E.g.f. x*(1-2*x-2*x^2-sqrt(1-4*x-4*x^2))/ (2*(1+x)^2). 0
0, 0, 0, 6, 48, 840, 17280, 448560, 13789440, 491702400, 19929369600, 904873939200, 45486949939200, 2507639957222400, 150419515915468800, 9752720435377920000, 679630757528346624000, 50655177765863903232000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Table of n, a(n) for n=0..17.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 700

FORMULA

D-finite with recurrence: a(1)=0, a(2)=0, a(3)=6, (-4*n^4-24*n-24*n^3-44*n^2)*a(n) +(-8*n^3-42*n^2-12-58*n)*a(n+1) +(-3*n^2-8*n+3)*a(n+2) +(n+2)*a(n+3)=0, a(4)=48, a(5)=840, a(6)=17280.

a(n) ~ sqrt(58-41*sqrt(2))*(1+sqrt(2))^(n-1)*2^n*n^(n-1)*exp(-n). - Vaclav Kotesovec, Aug 18 2013

a(n)= n!*A052705(n-1). - R. J. Mathar, Oct 26 2013

MAPLE

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

CROSSREFS

Sequence in context: A138426 A291104 A108092 * A267620 A275334 A192769

Adjacent sequences:  A052741 A052742 A052743 * A052745 A052746 A052747

KEYWORD

easy,nonn

AUTHOR

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

STATUS

approved

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Last modified September 26 16:15 EDT 2021. Contains 347670 sequences. (Running on oeis4.)