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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. 2
1, 1, 2, 8, 42, 273, 1970, 15368, 126510, 1086546, 9652364, 88172609, 824506191, 7865294687, 76331857094, 751981532942, 7506432993145, 75811326673326, 773682540353704, 7969986193751019, 82798726340037900, 866804540900696571 (list; graph; refs; listen; history; internal format)
OFFSET

0,3

COMMENTS

Symmetry group has order 4.

FORMULA

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

CROSSREFS

Sequence in context: A005315 A121635 A002874 * A052646 A002856 A093461

Adjacent sequences:  A078589 A078590 A078591 * A078593 A078594 A078595

KEYWORD

nonn

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com) and Jon Wild (wild(AT)music.mcgill.ca), Dec 08 2002

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Last modified February 17 18:15 EST 2012. Contains 206061 sequences.