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Search: id:A052633
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| A052633 |
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A simple regular expression in a labeled universe. |
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+0
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; listen)
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OFFSET
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0,3
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 579
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FORMULA
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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, a(4)=96}
n*n!
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MAPLE
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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
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Essentially the same as A001563.
Sequence in context: A070171 A036800 A157052 this_sequence A052638 A127553 A055357
Adjacent sequences: A052630 A052631 A052632 this_sequence A052634 A052635 A052636
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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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