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A209067
Number of n-bead necklaces labeled with numbers -2..2 not allowing reversal, with sum zero and avoiding the pattern z z+1 z+2.
0
1, 3, 6, 22, 70, 265, 1007, 4055, 16593, 69429, 294509, 1265692, 5494398, 24065829, 106207739, 471840078, 2108406146, 9470071142, 42731427358, 193612759011, 880517540867
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OFFSET
1,2
COMMENTS
Column 2 of
A209073
.
LINKS
Table of n, a(n) for n=1..21.
EXAMPLE
Some solutions for n=6:
.-2...-2...-2...-2...-2...-2...-1...-2...-2...-2...-2...-2...-2...-2...-2...-1
..1...-1....2....1...-1....1...-1...-1....2....0....1....1....0...-2...-1...-1
..2....1....0....0...-1....0....1...-2...-1...-1....1...-1....0...-2....2....0
..0....1...-1....1....2....2...-1....1....2....1....0....1....1....2...-1....0
..0...-1....2...-2....1....0....0....2....0....0...-2....1....1....2....0....0
.-1....2...-1....2....1...-1....2....2...-1....2....2....0....0....2....2....2
CROSSREFS
Sequence in context:
A380061
A049415
A208939
*
A389295
A220166
A220167
Adjacent sequences:
A209064
A209065
A209066
*
A209068
A209069
A209070
KEYWORD
nonn
AUTHOR
R. H. Hardin
, Mar 04 2012
STATUS
approved
