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Search: id:A052679
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| A052679 |
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A simple regular expression in a labeled universe. |
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+0
1
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| 1, 0, 0, 6, 0, 120, 720, 5040, 80640, 725760, 10886400, 159667200, 2395008000, 43589145600, 784604620800, 15692092416000, 334764638208000, 7469435990016000, 179266463760384000, 4500868715126784000
(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 627
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FORMULA
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E.g.f.: (-1+x^2)/(-1+x^2+x^3)
Recurrence: {a(1)=0, a(0)=1, a(2)=0, (-11*n-6-n^3-6*n^2)*a(n)+(-n^2-5*n-6)*a(n+1)+a(n+3)}
Sum(1/23*(-6+9*_alpha+4*_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, Z, Z, Sequence(Prod(Z, Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
restart: G(x):=(1-x-x^2)/(-1+x^2+x^3): f[0]:=G(x): for n from 1 to 30 do f[n]:=diff(f[n-1], x) od: x:=0: seq(f[n]/n, n=1..20); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 27 2009]
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CROSSREFS
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Sequence in context: A085511 A005212 A167028 this_sequence A134680 A111372 A156444
Adjacent sequences: A052676 A052677 A052678 this_sequence A052680 A052681 A052682
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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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