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A208726 Number of 2n-bead necklaces labeled with numbers 1..7 not allowing reversal, with neighbors differing by exactly 1. 2
6, 11, 20, 45, 104, 290, 796, 2366, 7076, 21684, 66996, 209594, 659560, 2090590, 6659120, 21312716, 68476512, 220798322, 714144612, 2316303916, 7531662344, 24545750474, 80160395804, 262280793024, 859662037240, 2822180991508, 9278652591844, 30547892144882 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

EXAMPLE

All solutions for n=2:

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

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

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

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

CROSSREFS

Column 7 of A208727.

Sequence in context: A021011 A000382 A208670 * A192750 A000383 A205540

Adjacent sequences:  A208723 A208724 A208725 * A208727 A208728 A208729

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 01 2012

EXTENSIONS

a(13)-a(28) from Andrew Howroyd, Mar 18 2017

STATUS

approved

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Last modified December 11 05:41 EST 2017. Contains 295868 sequences.