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Search: id:A052966
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| A052966 |
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A simple regular expression. |
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+0
1
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| 1, 0, 4, 2, 18, 18, 86, 122, 430, 746, 2222, 4346, 11742, 24682, 62958, 138202, 340670, 767562, 1853838, 4242746, 10122974, 23386282, 55392686, 128691866, 303490046, 707472138, 1664048590, 3886957050, 9128207134, 21347938154
(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 1038
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FORMULA
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G.f.: -(-1+x)/(1-x-4*x^2+2*x^3)
Recurrence: {a(1)=0, a(0)=1, a(2)=4, 2*a(n)-4*a(n+1)-a(n+2)+a(n+3)}
Sum(-1/79*(-1-36*_alpha+15*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(1-_Z-4*_Z^2+2*_Z^3))
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MAPLE
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spec := [S, {S=Sequence(Prod(Union(Prod(Sequence(Z), Z), Z), Union(Z, Z)))}, unlabeled ]: seq(combstruct[count ](spec, size=n), n=0..20);
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CROSSREFS
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Adjacent sequences: A052963 A052964 A052965 this_sequence A052967 A052968 A052969
Sequence in context: A122749 A074676 A117692 this_sequence A081797 A016517 A100400
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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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