A209109 Number of n-bead necklaces labeled with numbers -2..2 not allowing reversal, with sum zero and avoiding the patterns z z+1 z+2 and z z-1 z-2.

1, 3, 5, 22, 63, 238, 865, 3417, 13607, 55669, 230581, 968550, 4108547, 17589348, 75872175, 329480644, 1439151627, 6318822750, 27872030921, 123452835089

Offset

1,2

Comments

Column 2 of A209115.

Links

Table of n, a(n) for n=1..20.

Example

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

Crossrefs

Sequence in context: A025117 A318076 A124423 * A212260 A178377 A270621

Adjacent sequences: A209106 A209107 A209108 * A209110 A209111 A209112

Keyword

nonn

Author

R. H. Hardin, Mar 05 2012

Status

approved