A078592 Call two meanders from A005316 with 2n crossings equivalent if they differ by reflections in the X or Y axes. Sequence gives number of inequivalent meanders.

1, 1, 2, 8, 42, 273, 1970, 15368, 126510, 1086546, 9652364, 88172609, 824506191, 7865294687, 76331857094, 751981532942, 7506432993145, 75811326673326, 773682540353704, 7969986193751019, 82798726340037900, 866804540900696571

Offset

0,3

Comments

Symmetry group has order 4.

Links

Jean-François Alcover, Table of n, a(n) for n = 0..27

Formula

a(n) = (A005316(2n)+A005316(n))/2.

Mathematica

A005316 = Cases[Import["https://oeis.org/A005316/b005316.txt", "Table"], {_, _}][[All, 2]];
a[n_] := (A005316[[2 n + 1]] + A005316[[n + 1]])/2;
a /@ Range[0, 27] (* Jean-François Alcover, Sep 20 2019 *)

Crossrefs

Sequence in context: A002874 A324961 A351814 * A225108 A052646 A352646

Adjacent sequences: A078589 A078590 A078591 * A078593 A078594 A078595

Keyword

nonn

Author

N. J. A. Sloane and Jon Wild, Dec 08 2002

Status

approved