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Search: id:A052664
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| A052664 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 1, 10, 60, 768, 9480, 161280, 2968560, 65036160, 1568004480, 42507763200, 1259454873600, 40850693452800, 1432712945664000, 54168492771993600, 2193096759549696000, 94738664609132544000, 4347659200973856768000
(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 611
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FORMULA
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E.g.f.: -(-1+x)/(1-2*x-3*x^2+3*x^3)
Recurrence: {a(1)=1, a(0)=1, a(2)=10, (3*n^3+18*n^2+33*n+18)*a(n)+(-18-3*n^2-15*n)*a(n+1)+(-2*n-6)*a(n+2)+a(n+3)}
Sum(-1/107*(-13-38*_alpha+33*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(1-2*_Z-3*_Z^2+3*_Z^3))*n!
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Union(Z, Z, 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: A002493 A054364 A004309 this_sequence A090373 A041184 A089034
Adjacent sequences: A052661 A052662 A052663 this_sequence A052665 A052666 A052667
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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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