A209479 Number of n-bead necklaces labeled with numbers -2..2 allowing reversal, with sum zero and avoiding the patterns z z+1 z+2 and z z-1 z-2.

1, 3, 4, 15, 38, 136, 458, 1781, 6912, 28141, 115761, 485607, 2056341, 8800541, 37945282, 164766522, 719617100, 3159529303, 13936202144

Offset

1,2

Comments

Column 2 of A209485.

Links

Table of n, a(n) for n=1..19.

Example

Some solutions for n=10:
.-2...-2...-2...-2...-2...-2...-2...-2...-2...-2...-2...-2...-2...-2...-2...-2
.-1....0...-2...-2....0...-1...-1...-2...-1...-2...-2...-2...-1....1....0....0
..1...-1....0....1....0...-1....1....0....2...-1....0...-1...-1...-1...-1....0
.-2...-1....0....2...-2....2...-2...-2....0....2....1....1...-1....0....2....2
.-1....0....2...-1....0....0....2....2...-1....1....1....2....2....0...-2...-1
..2...-1...-1...-2....2....0....2....1....1...-2....2....2....0....2....2....0
..0....2....2....1....1....1...-2...-1....1....0....2....2....2...-1....2...-1
..2....2...-2....2....2....1....0....0....1....2...-2...-1....2....0...-1...-1
..0....0....2...-1...-2....0....1....2...-2....2...-1...-1...-1...-1...-1....2
..1....1....1....2....1....0....1....2....1....0....1....0....0....2....1....1

Crossrefs

Sequence in context: A041665 A052133 A332051 * A209338 A127144 A042771

Adjacent sequences: A209476 A209477 A209478 * A209480 A209481 A209482

Keyword

nonn

Author

R. H. Hardin, Mar 09 2012

Status

approved