A208963 Number of n-bead necklaces labeled with numbers -1..1 allowing reversal, with sum zero and first and second differences in -1..1.

1, 1, 1, 1, 1, 2, 2, 4, 4, 7, 7, 14, 16, 32, 46, 90, 140, 258, 416, 746, 1245, 2228, 3845, 6929, 12194, 21990, 39113, 70544, 126293, 228168, 410887, 744377, 1346837, 2446229, 4441502, 8084433, 14717678, 26841848, 48977823, 89494630, 163634188, 299532409

Offset

1,6

Links

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

Example

All solutions for n=8:
.-1...-1....0...-1
.-1...-1....0...-1
..0....0....0...-1
..0....0....0....0
..1....0....0....1
..1....1....0....1
..0....1....0....1
..0....0....0....0

Crossrefs

Column 1 of A208970.

Sequence in context: A355195 A325098 A368688 * A011142 A232047 A060029

Adjacent sequences: A208960 A208961 A208962 * A208964 A208965 A208966

Keyword

nonn

Author

R. H. Hardin, Mar 03 2012

Extensions

a(34)-a(42) from Andrew Howroyd, Mar 12 2017

Status

approved