A259974 Irregular triangle read by rows: T(n,k) = number of meanders with n bridges in which the first bridge is bridge k.

1, 1, 1, 1, 2, 1, 3, 2, 3, 8, 3, 3, 14, 7, 7, 14, 42, 14, 11, 14, 81, 36, 28, 36, 81, 262, 81, 57, 57, 81, 538, 221, 155, 155, 221, 538, 1828, 538, 353, 316, 353, 538, 3926, 1530, 1003, 902, 1003, 1530, 3926, 13820, 3926, 2458, 2053, 2053, 2458, 3926, 30694, 11510, 7214, 6059, 6059, 7214, 11510, 30694, 110954, 30694, 18575, 14810, 13827, 14810, 18575, 30694

Offset

1,5

References

Lando, S. K. and Zvonkin, A. K. Plane and projective meanders. Conference on Formal Power Series and Algebraic Combinatorics (Bordeaux, 1991).

Lando, S. K. and Zvonkin, A. K. Meanders. In Selected translations. Selecta Math. Soviet. 11 (1992), no. 2, 117-144.

Links

Andrew Howroyd, Table of n, a(n) for n = 1..420

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)

S. K. Lando and A. K. Zvonkin, Plane and projective meanders, Theoretical Computer Science Vol. 117 (1993), no. 1-2, 227-241.

Example

Triangle begins:
1,
1,
1,1,
2,1,
3,2,3,
8,3,3,
14,7,7,14,
42,14,11,14,
81,36,28,36,81,
262,81,57,57,81,
538,221,155,155,221,538,
...

Crossrefs

Diagonals are A005316, A006660, A006661, A006662. Cf. A008828.

Sequence in context: A297367 A118010 A318730 * A243561 A135550 A035491

Adjacent sequences: A259971 A259972 A259973 * A259975 A259976 A259977

Keyword

nonn,tabf

Author

N. J. A. Sloane, Jul 12 2015

Extensions

T(12,k)-T(40,k) from Andrew Howroyd, Dec 15 2015

Status

approved