A209343 Number of n-bead necklaces labeled with numbers -7..7 allowing reversal, with sum zero with no three beads in a row equal.

1, 8, 31, 311, 3045, 34720, 409199, 5016681, 62896466, 803647811, 10420410009, 136780924152

Offset

1,2

Comments

Column 7 of A209344.

Links

Table of n, a(n) for n=1..12.

Example

Some solutions for n=6:
.-5...-6...-7...-7...-3...-6...-7...-6...-6...-7...-7...-6...-7...-6...-5...-5
.-1....3...-2....0...-2...-5....3...-1...-3...-1...-2...-4...-5...-2...-4....0
.-1...-4....4...-1....7....6...-1....3....1....0....2....3....2....2....3....0
..5...-1....5....0...-1....6...-1....4....3....4....1....3...-3....4...-1...-3
.-1....3...-7....1...-2...-2....1....0....4...-1....3....1....7...-5....2....2
..3....5....7....7....1....1....5....0....1....5....3....3....6....7....5....6

Crossrefs

Sequence in context: A232621 A303176 A209484 * A270523 A332916 A270353

Adjacent sequences: A209340 A209341 A209342 * A209344 A209345 A209346

Keyword

nonn

Author

R. H. Hardin, Mar 06 2012

Status

approved