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Search: id:A052641
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| A052641 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 2, 14, 132, 1704, 27360, 527760, 11874240, 305343360, 8833224960, 283928198400, 10038995366400, 387222498432000, 16180539927552000, 728132005791590400, 35106736224688128000, 1805508406018437120000
(list; graph; listen)
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OFFSET
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0,2
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 587
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FORMULA
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E.g.f.: -(-1+x)/(1-3*x-x^2+x^3)
Recurrence: {a(0)=1, a(1)=2, a(2)=14, (n^3+6*n^2+11*n+6)*a(n)+(-n^2-5*n-6)*a(n+1)+(-3*n-9)*a(n+2)+a(n+3)}
Sum(-1/74*(-11-16*_alpha+7*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(1-3*_Z-_Z^2+_Z^3))*n!
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Union(Z, Sequence(Z), Sequence(Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A146971 A048990 A089602 this_sequence A157085 A073553 A144097
Adjacent sequences: A052638 A052639 A052640 this_sequence A052642 A052643 A052644
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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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