A209480 Number of n-bead necklaces labeled with numbers -3..3 allowing reversal, with sum zero and avoiding the patterns z z+1 z+2 and z z-1 z-2.

1, 4, 7, 35, 140, 731, 3740, 20888, 118137, 687981, 4059192, 24292229, 146840708, 895753665, 5505619880, 34065921090

Offset

1,2

Comments

Column 3 of A209485.

Links

Table of n, a(n) for n=1..16.

Example

Some solutions for n=8:
.-3...-2...-3...-3...-3...-3...-3...-3...-3...-2...-3...-3...-3...-3...-3...-3
.-2...-2...-1...-1....0...-3....1....0...-1...-1...-2....0...-1...-1...-2...-3
..0....0...-3....1...-1...-1...-1...-2....2...-2....0....3....2....0....1...-1
..3....3....1....1....3...-1...-2....2....3...-1....1...-2....0...-3...-1....3
..3...-2....2....1....2....3....1....3....1....3....3....2....2....2...-2....3
.-2....1....0....0....0....1....1....1....0....0....2....2....1...-1....3...-3
..1....0....2....0...-3....2....2...-2...-3....0...-3...-3...-2....3....3....1
..0....2....2....1....2....2....1....1....1....3....2....1....1....3....1....3

Crossrefs

Sequence in context: A140981 A283819 A124624 * A209339 A212500 A302198

Adjacent sequences: A209477 A209478 A209479 * A209481 A209482 A209483

Keyword

nonn

Author

R. H. Hardin, Mar 09 2012

Status

approved