A209481 Number of n-bead necklaces labeled with numbers -4..4 allowing reversal, with sum zero and avoiding the patterns z z+1 z+2 and z z-1 z-2.

1, 5, 12, 72, 390, 2606, 17771, 128598, 950292, 7180767, 55056590, 427567892, 3354737555, 26555548849

Offset

1,2

Comments

Column 4 of A209485.

Links

Table of n, a(n) for n=1..14.

Example

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

Crossrefs

Sequence in context: A297644 A242043 A156236 * A209340 A128323 A202203

Adjacent sequences: A209478 A209479 A209480 * A209482 A209483 A209484

Keyword

nonn

Author

R. H. Hardin, Mar 09 2012

Status

approved