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Search: id:A052597
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| A052597 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 0, 2, 6, 24, 240, 1440, 15120, 161280, 1814400, 25401600, 359251200, 5748019200, 99632332800, 1830744115200, 36614882304000, 774143225856000, 17428683976704000, 416154290872320000, 10461478635159552000
(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 542
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FORMULA
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E.g.f.: -1/(-1+x^2+x^3)
Recurrence: {a(1)=0, a(0)=1, a(2)=2, (-11*n-6-n^3-6*n^2)*a(n)+(-n^2-5*n-6)*a(n+1)+a(n+3)}
Sum(-1/23*(-3-7*_alpha+2*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(_Z^3+_Z^2-1))*n!
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Union(Z, Prod(Z, Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A034874 A052699 A074351 this_sequence A052632 A052692 A052723
Adjacent sequences: A052594 A052595 A052596 this_sequence A052598 A052599 A052600
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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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