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A052628 E.g.f. (2+x^3-x^4)/(1-x). 1
2, 2, 4, 18, 48, 240, 1440, 10080, 80640, 725760, 7257600, 79833600, 958003200, 12454041600, 174356582400, 2615348736000, 41845579776000, 711374856192000, 12804747411456000, 243290200817664000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Table of n, a(n) for n=0..19.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 574

FORMULA

E.g.f.: (-2+x^4-x^3)/(-1+x)

Recurrence: {(-1-n)*a(n)+a(n+1)=0, a(2)=4, a(1)=2, a(0)=2, a(4)=48, a(3)=18}

2*n!, n != 3.

MAPLE

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

MATHEMATICA

With[{nn=20}, CoefficientList[Series[(2+x^3-x^4)/(1-x), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Feb 03 2015 *)

CROSSREFS

Sequence in context: A079556 A232161 A335684 * A006853 A120417 A175185

Adjacent sequences:  A052625 A052626 A052627 * A052629 A052630 A052631

KEYWORD

easy,nonn

AUTHOR

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

STATUS

approved

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Last modified May 10 05:05 EDT 2021. Contains 343748 sequences. (Running on oeis4.)