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A052633
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E.g.f. x^2*(1+x-x^2)/(1-x)^2.
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1
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0, 0, 2, 18, 96, 600, 4320, 35280, 322560, 3265920, 36288000, 439084800, 5748019200, 80951270400, 1220496076800, 19615115520000, 334764638208000, 6046686277632000, 115242726703104000, 2311256907767808000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 579
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FORMULA
| E.g.f.: -x^2*(-x+x^2-1)/(-1+x)^2
Recurrence: {a(1)=0, a(0)=0, a(2)=2, a(3)=18, (-n^2-2*n-1)*a(n)+a(n+1)*n=0, a(4)=96}
n*n!, n>2.
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MAPLE
| spec := [S, {S=Prod(Z, Z, Sequence(Z), Union(Z, Sequence(Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
restart:printlevel := -1; a := [0]; T := x->LambertW(-x); f := series(((1+T(x)))/(1-T(x)), x, 24); for m from 1 to 19 do a := [op(a), op(2*m, f)*m! ] od; print(a); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 28 2009]
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CROSSREFS
| Essentially the same as A001563.
Sequence in context: A206623 A036800 A157052 * A052638 A127553 A173785
Adjacent sequences: A052630 A052631 A052632 * A052634 A052635 A052636
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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