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A006657
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Closed meanders with 2 components and 2n bridges.
(Formerly M2037)
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2
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2, 12, 84, 640, 5236, 45164, 406012, 3772008, 35994184, 351173328, 3490681428, 35253449296, 360946635312, 3739935635756, 39159200588780, 413836299216608, 4409705753032648, 47337525317450816, 511563350415103008
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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2,1
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REFERENCES
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S. K. Lando and A. K. Zvonkin "Plane and projective meanders", Séries Formelles et Combinatoire Algébrique. Laboratoire Bordelais de Recherche Informatique, Université Bordeaux I, 1991, pp. 287-303.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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Table of n, a(n) for n=2..20.
P. Di Francesco, O. Golinelli and E. Guitter, Meander, folding and arch statistics, arXiv:hep-th/9506030, 1995.
S. K. Lando and A. K. Zvonkin , Plane and projective meanders, Séries Formelles et Combinatoire Algébrique. Laboratoire Bordelais de Recherche Informatique, Université Bordeaux I, 1991, pp. 287-303. (Annotated scanned copy)
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MATHEMATICA
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A008828 = Import["https://oeis.org/A008828/b008828.txt", "Table"][[All, 2]];
a[n_] := A008828[[(n^2 - n + 4)/2]];
a /@ Range[2, 20] (* Jean-François Alcover, Sep 25 2019 *)
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CROSSREFS
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Cf. A005315.
A column of triangle A008828.
Sequence in context: A130464 A319326 A214765 * A105927 A316702 A235351
Adjacent sequences: A006654 A006655 A006656 * A006658 A006659 A006660
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KEYWORD
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nonn,nice
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AUTHOR
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N. J. A. Sloane, Simon Plouffe
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EXTENSIONS
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a(13)-a(20) from Andrew Howroyd, Nov 22 2015
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STATUS
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approved
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