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A209026 Number of n-bead necklaces labeled with numbers -2..2 allowing reversal, with sum zero and first differences in -2..2. 1
1, 2, 2, 6, 11, 33, 86, 278, 873, 2938, 9904, 34321, 119673, 422725, 1502590, 5381671, 19377063, 70138385, 254978018, 930709334, 3409356533, 12530190100, 46188325542, 170723964752, 632624262841, 2349655631568, 8745690221340, 32617408075856 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

EXAMPLE

Some solutions for n=6:

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

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

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

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

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

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

CROSSREFS

Column 2 of A209032.

Sequence in context: A299018 A269830 A275312 * A091764 A335311 A192933

Adjacent sequences:  A209023 A209024 A209025 * A209027 A209028 A209029

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 04 2012

EXTENSIONS

a(22)-a(28) from Andrew Howroyd, Mar 19 2017

STATUS

approved

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Last modified July 8 07:16 EDT 2020. Contains 335513 sequences. (Running on oeis4.)