A209027 Number of n-bead necklaces labeled with numbers -3..3 allowing reversal, with sum zero and first differences in -3..3.

1, 2, 4, 12, 34, 144, 576, 2613, 11841, 55773, 265095, 1280476, 6238246, 30674021, 151874427, 756842052, 3792315084, 19096602857, 96586072494, 490453174481, 2499410534082, 12778951549191, 65530990963959, 336965088080673, 1737060054201011, 8975377470866966

Offset

1,2

Links

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

Example

Some solutions for n=6:
.-2...-3...-3...-3...-2...-1...-1...-3...-3...-3...-2...-1...-3...-1...-1...-1
..0...-2...-1...-2...-1...-1....1....0....0...-1....0....0...-2...-1...-1...-1
..0....1....1....1....0....2...-1...-1....0....0....2...-1....1...-1....0....0
..2....2....2....1....0...-1....1....2....0....2....0....0....3....2....1...-1
..0....2....1....3....3...-1...-1....2....3....2...-1....0....2...-1....1....2
..0....0....0....0....0....2....1....0....0....0....1....2...-1....2....0....1

Crossrefs

Column 3 of A209032.

Sequence in context: A245310 A363202 A215953 * A069727 A148204 A151525

Adjacent sequences: A209024 A209025 A209026 * A209028 A209029 A209030

Keyword

nonn

Author

R. H. Hardin, Mar 04 2012

Extensions

a(19)-a(26) from Andrew Howroyd, Mar 19 2017

Status

approved