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A052628
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E.g.f. (2+x^3-x^4)/(1-x).
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1
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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; internal format)
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OFFSET
| 0,1
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 574
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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.
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MAPLE
| spec := [S, {S=Union(Sequence(Z), Sequence(Z), Prod(Z, Z, Z))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A070282 A051285 A079556 * A006853 A120417 A175185
Adjacent sequences: A052625 A052626 A052627 * A052629 A052630 A052631
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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