

A209026


Number of nbead 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
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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



