0,3

Number of ways to fold a strip of n+1 labeled stamps.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

I. Jensen, A transfer matrix approach to the enumeration of plane meanders. J. Phys. A 33, 5953-5963 (2000).

I. Jensen and A. J. Guttmann, Critical exponents of plane meanders. J. Phys. A 33, L187-L192 (2000).

J. E. Koehler, Folding a strip of stamps, J. Combin. Theory, 5 (1968), 135-152.

W. F. Lunnon, A map-folding problem, Math. Comp. 22 (1968), 193-199.

A. Sade, Sur les Chevauchements des Permutations, published by the author, Marseille, 1949.

J. Touchard, Contributions a` l'e'tude du proble`me des timbres postes, Canad. J. Math., 2 (1950), 385-398.

I. Jensen, Table of n, a(n) for n = 1..45

P. Di Francesco, O. Golinelli and E. Guitter, Meander, folding and arch statistics.

P. Di Francesco, O. Golinelli and E. Guitter, Meanders: a direct enumeration approach, Nucl. Phys. B 482 [ FS ] (1996) 497-535.

I. Jensen, Home page

I. Jensen, More terms

Index entries for sequences obtained by enumerating foldings

P. Di Francesco, Matrix model combinatorics: applications to folding and coloring

M. La Croix, Approaches to the Enumerative Theory of Meanders [From Gerald McGarvey (gerald.mcgarvey(AT)comcast.net), Oct 26 2008]

a(3) = 4: the four solutions with three crossings are the two solutions shown in A086441 together with their reflections about a North-South axis.

A000560(n) = a(n)/2 (for n >= 2) gives number of nonisomorphic solutions (see also A086441). Cf. A001011, A001997.

Sequence in context: A084078 A137842 A049146 this_sequence A001997 A000084 A057734

Adjacent sequences: A000679 A000680 A000681 this_sequence A000683 A000684 A000685

nonn,nice

N. J. A. Sloane (njas(AT)research.att.com).

Sade gives the first 11 terms. Computed to n = 45 by Iwan Jensen.