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Search: id:A052614
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| A052614 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 1, 2, 6, 48, 240, 1440, 10080, 120960, 1088640, 10886400, 119750400, 1916006400, 24908083200, 348713164800, 5230697472000, 104613949440000, 1778437140480000, 32011868528640000, 608225502044160000
(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 559
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FORMULA
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E.g.f.: 1/(-1+x)/(-1+x^4)
Recurrence: {a(1)=1, a(0)=1, a(3)=6, a(2)=2, (-61*n-11*n^3-n^4-30-41*n^2)*a(n)+(-n^2-5*n-6)*a(n+1)+(-n-3)*a(n+2)+a(n+4)-a(n+3)}
(Sum(1/16*(2*_alpha+_alpha^2-1)*_alpha^(-1-n), _alpha=RootOf(1+_Z+_Z^2+_Z^3))+1/4*n+5/8)*n!
n!*[n/4+1].
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MAPLE
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spec := [S, {S=Prod(Sequence(Z), Sequence(Prod(Z, Z, Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A072444 A052596 A098710 this_sequence A052688 A052657 A092143
Adjacent sequences: A052611 A052612 A052613 this_sequence A052615 A052616 A052617
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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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