A208987 - OEIS

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A208987

Number of n-bead necklaces labeled with numbers -2..2 not allowing reversal, with sum zero and first differences in -2..2.

1, 2, 3, 7, 17, 51, 155, 508, 1683, 5709, 19581, 68047, 238513, 843280, 3002105, 10755341, 38742697, 140247035, 509913321, 1861307488, 6818552671, 25059962507, 92376046425, 341446354053

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

Column 2 of A208993.

LINKS

Table of n, a(n) for n=1..24.

EXAMPLE

Some solutions for n=6:

.-1...-2...-1...-1...-2...-2...-1...-1...-2...-2...-2...-1...-2...-1...-1...-2

..0....0...-1....1....0....0....0....0....0....0...-2...-1....0...-1....0....0

..0....2...-1....0....2....1...-1....1....0....2....0....1....1....1....1....1

..1....1....0....0....0....2....1...-1....2....0....2...-1....1....0....0....0

..0....0....2....0....1....0....0....1....1....0....2....1....0....1....0....1

..0...-1....1....0...-1...-1....1....0...-1....0....0....1....0....0....0....0

CROSSREFS

Sequence in context: A173868 A274291 A358456 * A176074 A281368 A330726

Adjacent sequences: A208984 A208985 A208986 * A208988 A208989 A208990

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 04 2012

STATUS

approved