A060206 Number of rotationally symmetric closed meanders of length 4n+2.

1, 2, 10, 66, 504, 4210, 37378, 346846, 3328188, 32786630, 329903058, 3377919260, 35095839848, 369192702554, 3925446804750, 42126805350798, 455792943581400, 4967158911871358, 54480174340453578, 600994488311709056, 6664356253639465480

Offset

0,2

Comments

Closed meanders of other lengths do not have rotational symmetry. - Andrew Howroyd, Nov 24 2015

See A077460 for additional information on the symmetries of closed meanders.

Links

Table of n, a(n) for n=0..20.

R. Bacher, Meander algebras

Andrew Howroyd, Illustration of a(1) and a(2)

Formula

a(n) = A000682(2n + 1). - Andrew Howroyd, Nov 24 2015

Mathematica

A000682 = Import["https://oeis.org/A000682/b000682.txt", "Table"][[All, 2]];
a[n_] := A000682[[2n + 1]];
a /@ Range[0, 20] (* Jean-François Alcover, Sep 03 2019 *)

Crossrefs

Cf. A000682, A005315, A077055, A077460, A223096.

Meander sequences in Bacher's paper: A060066, A060089, A060111, A060148, A060149, A060174, A060198.

Sequence in context: A379330 A278460 A278462 * A277493 A361448 A376226

Adjacent sequences: A060203 A060204 A060205 * A060207 A060208 A060209

Keyword

nonn,nice

Author

N. J. A. Sloane, Apr 10 2001

Extensions

Name edited by Andrew Howroyd, Nov 24 2015

a(7)-a(20) from Andrew Howroyd, Nov 24 2015

Status

approved