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A208720 Number of n-bead necklaces labeled with numbers 1..7 allowing reversal, with no adjacent beads differing by more than 1. 1
7, 13, 19, 36, 58, 122, 224, 502, 1066, 2528, 5902, 14717, 36557, 93987, 242387, 635990, 1675743, 4457771, 11903835, 31970464, 86144382, 233001926, 631920076, 1718567054, 4684178054, 12794677456, 35012475762, 95976563897, 263496604025, 724445459431 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

a(2n+1) = (1/2) * (A208776(2n+1) + A002714(n+1)). - Andrew Howroyd, Mar 03 2017

a(2n) = (1/2) * A208776(2n) + (1/4) * (A002714(n) + A002714(n+1)). - Andrew Howroyd, Mar 03 2017

EXAMPLE

All solutions for n=3:

..1....1....6....3....6....5....2....4....4....3....5....4....5....7....6....2

..2....1....6....4....7....5....3....4....5....3....6....4....5....7....6....2

..2....1....7....4....7....5....3....5....5....3....6....4....6....7....6....3

..

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

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

..2....2....4

CROSSREFS

Column 7 of A208721.

Cf. A208776, A002714.

Sequence in context: A283191 A048375 A198035 * A208776 A108295 A071923

Adjacent sequences:  A208717 A208718 A208719 * A208721 A208722 A208723

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 01 2012

EXTENSIONS

a(22)-a(30) from Andrew Howroyd, Mar 03 2017

STATUS

approved

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Last modified September 22 20:30 EDT 2018. Contains 315270 sequences. (Running on oeis4.)