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Search: id:A052982
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| A052982 |
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A simple regular expression. |
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+0
1
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| 1, 1, 4, 10, 27, 73, 196, 528, 1421, 3825, 10296, 27714, 74599, 200801, 540504, 1454896, 3916201, 10541393, 28374684, 76377258, 205587683, 553388489, 1489577660, 4009555040, 10792677717, 29051077025, 78197931824
(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 1055
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FORMULA
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G.f.: -(-1+x)/(1-2*x-2*x^2+x^4)
Recurrence: {a(1)=1, a(0)=1, a(2)=4, a(3)=10, a(n)-2*a(n+2)-2*a(n+3)+a(n+4)}
Sum(-1/182*(-35*_alpha+2*_alpha^3+22*_alpha^2-25)*_alpha^(-1-n), _alpha=RootOf(1-2*_Z-2*_Z^2+_Z^4))
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MAPLE
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spec := [S, {S=Sequence(Prod(Union(Prod(Z, Z), Z), Union(Sequence(Z), Z)))}, unlabeled ]: seq(combstruct[count ](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A121494 A122744 A077923 this_sequence A108672 A000495 A027067
Adjacent sequences: A052979 A052980 A052981 this_sequence A052983 A052984 A052985
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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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