A208818 Number of n-bead necklaces labeled with numbers -1..1 allowing reversal, with sum zero.

1, 2, 2, 5, 7, 18, 32, 84, 185, 486, 1192, 3179, 8261, 22290, 59788, 163181, 445699, 1228686, 3396224, 9440759, 26322371, 73680058, 206822134, 582308320, 1643573625, 4650401810, 13186590962, 37469003353

Offset: 1

Author

R. H. Hardin, Mar 01 2012

Keywords

• nonn

Comments

Column 1 of A208825.

Examples

			All solutions for n=3:
..0...-1
..0....0
..0....1