A209336 Number of n-bead necklaces labeled with numbers -n..n allowing reversal, with sum zero with no three beads in a row equal.

1, 3, 7, 72, 883, 16968, 409199, 12099880, 420661470, 16838275108, 762821788869

Offset

1,2

Comments

Diagonal of A209344.

Links

Table of n, a(n) for n=1..11.

Example

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

Crossrefs

Sequence in context: A128072 A094008 A209477 * A078552 A091259 A354891

Adjacent sequences: A209333 A209334 A209335 * A209337 A209338 A209339

Keyword

nonn

Author

R. H. Hardin, Mar 06 2012

Status

approved