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Search: id:A052588
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| A052588 |
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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, 12, 48, 600, 5760, 65520, 967680, 14515200, 250387200, 4790016000, 98195328000, 2204365363200, 53178757632000, 1371750412032000, 37828404117504000, 1107254963662848000, 34316723062702080000
(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 533
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FORMULA
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E.g.f.: -(-1+x)/(1-x-x^3+x^4-x^2)
Recurrence: {a(1)=0, a(0)=1, a(2)=2, a(3)=12, (n^4+35*n^2+50*n+24+10*n^3)*a(n)+(-n^3-9*n^2-26*n-24)*a(n+1)+(-n^2-7*n-12)*a(n+2)+(-n-4)*a(n+3)+a(n+4)}
Sum(-1/39*(-2-11*_alpha+4*_alpha^2+_alpha^3)*_alpha^(-1-n), _alpha=RootOf(1-_Z-_Z^3+_Z^4-_Z^2))*n!
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Z, Union(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: A052591 A029766 A088311 this_sequence A139239 A060238 A085495
Adjacent sequences: A052585 A052586 A052587 this_sequence A052589 A052590 A052591
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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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