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Search: id:A052915
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| A052915 |
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A simple regular expression. |
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+0
1
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| 1, 0, 1, 4, 2, 9, 20, 23, 64, 120, 193, 436, 797, 1452, 2978, 5513, 10456, 20547, 38608, 73984, 142865, 271032, 520025, 997700, 1902226, 3646905, 6982156, 13342639, 25558832, 48907224, 93547505, 179103308, 342695989, 655720140, 1255083538
(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 897
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FORMULA
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G.f.: -(-1+x)/(1-x-3*x^3+3*x^4-x^2)
Recurrence: {a(1)=0, a(0)=1, a(3)=4, a(2)=1, 3*a(n)-3*a(n+1)-a(n+2)-a(n+3)+a(n+4)}
Sum(-1/2857*(-142-885*_alpha+351*_alpha^3+240*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(1-_Z-3*_Z^3+3*_Z^4-_Z^2))
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Z, Union(Sequence(Z), Z, Z, Z)))}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A104583 A097664 A144811 this_sequence A130273 A016516 A138569
Adjacent sequences: A052912 A052913 A052914 this_sequence A052916 A052917 A052918
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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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EXTENSIONS
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More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jun 06 2000
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