A209108 Number of n-bead necklaces labeled with numbers -1..1 not allowing reversal, with sum zero and avoiding the patterns z z+1 z+2 and z z-1 z-2.

1, 2, 1, 5, 5, 15, 25, 68, 139, 354, 813, 2047, 4935, 12421, 30833, 78102, 197139, 503132, 1284711, 3302155, 8503965, 21996761, 57026957, 148322398, 386626825, 1010375144, 2645762431, 6942725217, 18251279163, 48065184969, 126783827201

Offset

1,2

Comments

Column 1 of A209115.

Links

R. H. Hardin, Table of n, a(n) for n = 1..32

Example

All solutions for n=6:
.-1...-1...-1...-1...-1...-1...-1...-1...-1...-1....0...-1...-1...-1...-1
.-1...-1...-1....0....0....1....0....1...-1....1....0...-1....0...-1....0
..1....1....1....0....0...-1...-1....0...-1...-1....0....1....0....0....0
..1....1....0....1....0....1....1....0....1....1....0...-1....1....0...-1
..0...-1....0....0....0...-1....0....0....1....0....0....1...-1....1....1
..0....1....1....0....1....1....1....0....1....0....0....1....1....1....1

Crossrefs

Sequence in context: A086905 A167638 A317878 * A269019 A184234 A193816

Adjacent sequences: A209105 A209106 A209107 * A209109 A209110 A209111

Keyword

nonn

Author

R. H. Hardin, Mar 05 2012

Status

approved