A209026 Number of n-bead necklaces labeled with numbers -2..2 allowing reversal, with sum zero and first differences in -2..2.

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

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: A269830 A350114 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