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Search: id:A052970
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| A052970 |
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A simple regular expression. |
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+0
2
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| 1, 0, 2, 2, 8, 16, 44, 104, 264, 648, 1616, 4000, 9936, 24640, 61152, 151712, 376448, 934016, 2317504, 5750144, 14267264, 35399808, 87833856, 217932800, 540733696, 1341665280, 3328932352, 8259727872, 20493989888, 50849570816, 126167665664
(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 1042
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FORMULA
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G.f.: -(-1+2*x)/(1-2*x-2*x^2+2*x^3)
Recurrence: {a(1)=0, a(0)=1, a(2)=2, 2*a(n)-2*a(n+1)-2*a(n+2)+a(n+3)}
Sum(-1/37*(3-15*_alpha+2*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(2*_Z^3-2*_Z^2-2*_Z+1))
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MAPLE
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spec := [S, {S=Sequence(Prod(Union(Prod(Sequence(Union(Z, 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: A005633 A026585 A098273 this_sequence A109190 A016120 A085542
Adjacent sequences: A052967 A052968 A052969 this_sequence A052971 A052972 A052973
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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 05 2000
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