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A208818 Number of n-bead necklaces labeled with numbers -1..1 allowing reversal, with sum zero. 0
1, 2, 2, 5, 7, 18, 32, 84, 185, 486, 1192, 3179, 8261, 22290, 59788, 163181, 445699, 1228686, 3396224, 9440759, 26322371, 73680058, 206822134, 582308320, 1643573625, 4650401810, 13186590962, 37469003353 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 1 of A208825.

LINKS

Table of n, a(n) for n=1..28.

EXAMPLE

All solutions for n=3:

..0...-1

..0....0

..0....1

CROSSREFS

Sequence in context: A079280 A038750 A300439 * A221835 A074476 A224610

Adjacent sequences:  A208815 A208816 A208817 * A208819 A208820 A208821

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 01 2012

STATUS

approved

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Last modified October 14 00:32 EDT 2019. Contains 327991 sequences. (Running on oeis4.)