A006658 Closed meanders with 3 components and 2n bridges.

5, 56, 580, 5894, 60312, 624240, 6540510, 69323910, 742518832, 8028001566, 87526544560, 961412790002, 10630964761766, 118257400015312, 1322564193698320, 14863191405246888, 167771227744292160, 1901345329566422790

Offset: 3

Author

N. J. A. Sloane

Keywords

• nonn

References

• 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).

Links

• 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)

Crossrefs

Cf. A005315, A006657.

A column of triangle A008828.

Programs

Mathematica

A008828 = Import["https://oeis.org/A008828/b008828.txt", "Table"][[All, 2]];
a[n_] := A008828[[(n^2 - n + 6)/2]];
a /@ Range[3, 20] (* Jean-François Alcover, Sep 25 2019 *)

Extensions

a(13)-a(20) from Andrew Howroyd, Nov 22 2015