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Search: id:A052583
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| A052583 |
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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, 6, 24, 240, 2160, 25200, 322560, 4717440, 76204800, 1357171200, 26345088000, 554204851200, 12553673932800, 304688127744000, 7887891787776000, 216969331138560000, 6319142847553536000
(list; graph; listen)
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OFFSET
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0,4
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 527
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FORMULA
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E.g.f.: x*(-1+x)/(-1+x+x^2)
Recurrence: {a(1)=1, a(0)=0, a(2)=0, (-2-n^2-3*n)*a(n)+(-2-n)*a(n+1)+a(n+2)}
Sum(-1/5*(-3+4*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z+_Z^2))*n!
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MAPLE
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spec := [S, {S=Prod(Z, Sequence(Prod(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: A052594 A091097 A112675 this_sequence A052671 A052733 A010567
Adjacent sequences: A052580 A052581 A052582 this_sequence A052584 A052585 A052586
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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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