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A208771 Number of n-bead necklaces labeled with numbers 1..n not allowing reversal, with no adjacent beads differing by more than 1. 1
1, 3, 7, 18, 41, 117, 299, 861, 2413, 6955, 19943, 57974, 168013, 489789, 1428611, 4177232, 12226997, 35847123, 105200351, 309086838, 908931221, 2675276801, 7880255915, 23228969891, 68518137777, 202231890207, 597228362551, 1764663912122 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..100

EXAMPLE

All solutions for n=3:

..2....3....1....1....2....1....2

..3....3....2....1....2....1....2

..3....3....2....2....3....1....2

CROSSREFS

Diagonal of A208777.

Sequence in context: A026533 A131630 A305652 * A036884 A102291 A034691

Adjacent sequences:  A208768 A208769 A208770 * A208772 A208773 A208774

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 01 2012

EXTENSIONS

a(19)-a(28) from Andrew Howroyd, Mar 18 2017

STATUS

approved

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Last modified February 17 02:33 EST 2019. Contains 320200 sequences. (Running on oeis4.)