A209025 Number of n-bead necklaces labeled with numbers -1..1 allowing reversal, with sum zero and first differences in -1..1.

1, 1, 1, 2, 2, 4, 6, 13, 21, 45, 83, 181, 362, 794, 1676, 3703, 8049, 17925, 39679, 88980, 199308, 449714, 1015574, 2303940, 5234731, 11931095, 27239911, 62337821, 142894336, 328168558, 754815704, 1738888333, 4011453913, 9266702091, 21433240903, 49633242760

Offset: 1

Author

R. H. Hardin, Mar 04 2012

Keywords

• nonn

Examples

			All solutions for n=6:
..0...-1...-1...-1
..0....0...-1....0
..0....0....0....0
..0....1....1....0
..0....0....1....1
..0....0....0....0
		

Links

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

Crossrefs

Column 1 of A209032.

Extensions

a(33)-a(36) from Andrew Howroyd, Mar 19 2017