A208819 Number of n-bead necklaces labeled with numbers -2..2 allowing reversal, with sum zero.

1, 3, 5, 16, 45, 167, 609, 2471, 10143, 43223, 186533, 818836, 3629835, 16250859, 73300289, 332895316, 1520604469, 6981991345, 32205476541

Offset

1,2

Comments

Column 2 of A208825.

Links

Table of n, a(n) for n=1..19.

Example

All solutions for n=3:
.-2...-1...-1...-2....0
..1....0...-1....0....0
..1....1....2....2....0

Crossrefs

Sequence in context: A371868 A243321 A099101 * A038120 A192911 A105408

Adjacent sequences: A208816 A208817 A208818 * A208820 A208821 A208822

Keyword

nonn

Author

R. H. Hardin, Mar 01 2012

Status

approved