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A052576
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E.g.f. (1+x^2-2x^3)/(1-2x).
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0
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1, 2, 10, 48, 384, 3840, 46080, 645120, 10321920, 185794560, 3715891200, 81749606400, 1961990553600, 51011754393600, 1428329123020800, 42849873690624000, 1371195958099968000, 46620662575398912000
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listen;
history;
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OFFSET
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0,2
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LINKS
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Table of n, a(n) for n=0..17.
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 519
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FORMULA
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E.g.f.: (-x^2+2*x^3-1)/(-1+2*x)
Recurrence: {a(0)=1, a(1)=2, (-2*n-2)*a(n)+a(n+1)=0, a(2)=10, a(3)=48}
2^n*n!, n>2.
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MAPLE
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spec := [S, {S=Union(Prod(Z, Z), Sequence(Union(Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Essentially the same as A000165 (which is the main entry).
Sequence in context: A166922 A129118 A037256 * A219662 A143147 A218778
Adjacent sequences: A052573 A052574 A052575 * A052577 A052578 A052579
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KEYWORD
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easy,nonn
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AUTHOR
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encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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STATUS
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approved
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