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A052670 E.g.f. x^2/(1-4x). 0
0, 0, 2, 24, 384, 7680, 184320, 5160960, 165150720, 5945425920, 237817036800, 10463949619200, 502269581721600, 26118018249523200, 1462609021973299200, 87756541318397952000, 5616418644377468928000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..16.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 618

FORMULA

E.g.f.: -x^2/(-1+4*x)

Recurrence: {a(1)=0, a(0)=0, a(2)=2, (-4-4*n)*a(n)+a(n+1)=0}

4^(n-2)*n!, n>1.

MAPLE

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

MATHEMATICA

With[{nn=20}, CoefficientList[Series[x^2/(1-4x), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Sep 27 2015 *)

CROSSREFS

Sequence in context: A188953 A081685 A288944 * A052736 A103904 A219431

Adjacent sequences:  A052667 A052668 A052669 * A052671 A052672 A052673

KEYWORD

easy,nonn

AUTHOR

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

STATUS

approved

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Last modified July 8 01:48 EDT 2020. Contains 335502 sequences. (Running on oeis4.)