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Search: id:A052672
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| A052672 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 0, 4, 6, 120, 600, 10080, 95760, 1693440, 23950080, 475372800, 8821612800, 199743667200, 4533271142400, 116906088499200, 3112264995840000, 90679371374592000, 2757644630028288000, 89895729202126848000
(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 620
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FORMULA
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E.g.f.: -(-1+x)/(x^3-2*x^2-x+1)
Recurrence: {a(1)=0, a(0)=1, a(2)=4, (n^3+6*n^2+11*n+6)*a(n)+(-2*n^2-10*n-12)*a(n+1)+(-n-3)*a(n+2)+a(n+3)}
Sum(-1/7*_alpha*(-3+_alpha)*_alpha^(-1-n), _alpha=RootOf(_Z^3-2*_Z^2-_Z+1))*n!
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Union(Z, Prod(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: A012909 A012934 A013165 this_sequence A137025 A070155 A074124
Adjacent sequences: A052669 A052670 A052671 this_sequence A052673 A052674 A052675
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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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