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Search: id:A052604
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| A052604 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 1, 4, 30, 240, 2520, 32400, 478800, 8104320, 154586880, 3273177600, 76241088000, 1937561472000, 53340660172800, 1581414202368000, 50234310846720000, 1702089880178688000, 61276407362666496000
(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 549
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FORMULA
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E.g.f.: -(-1+x)/(1-2*x-x^3+x^4)
Recurrence: {a(1)=1, a(0)=1, a(2)=4, (n^4+35*n^2+50*n+24+10*n^3)*a(n)+(-n^3-9*n^2-26*n-24)*a(n+1)+(-2*n-8)*a(n+3)+a(n+4), a(3)=30}
Sum(-1/643*(-94-127*_alpha-22*_alpha^2+75*_alpha^3)*_alpha^(-1-n), _alpha=RootOf(1-2*_Z-_Z^3+_Z^4))*n!
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Union(Sequence(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: A000313 A082144 A137971 this_sequence A038225 A086452 A091527
Adjacent sequences: A052601 A052602 A052603 this_sequence A052605 A052606 A052607
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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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