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Search: id:A052605
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| A052605 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 0, 1, 0, 0, 24, 120, 720, 10080, 120960, 1451520, 21772800, 359251200, 6227020800, 118313395200, 2440992153600, 53614649088000, 1255367393280000, 31300493672448000, 825906208038912000
(list; graph; listen)
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OFFSET
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0,5
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 550
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FORMULA
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E.g.f.: x*(-1+x)/(-1+x+x^3)
Recurrence: {a(1)=1, a(0)=0, a(2)=0, (-11*n-6-n^3-6*n^2)*a(n)+(-n-3)*a(n+2)+a(n+3)}
Sum(1/31*(_alpha+11*_alpha^2-3)*_alpha^(-1-n), _alpha=RootOf(-1+_Z+_Z^3))*n!
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MAPLE
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spec := [S, {S=Prod(Z, Sequence(Prod(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: A050213 A124657 A052581 this_sequence A042120 A044356 A044737
Adjacent sequences: A052602 A052603 A052604 this_sequence A052606 A052607 A052608
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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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