A209001 Number of n-bead necklaces labeled with numbers -2..2 not allowing reversal, with sum zero and first and second differences in -2..2.

1, 1, 1, 3, 5, 10, 23, 66, 167, 445, 1171, 3167, 8569, 23618, 65589, 183955, 518183, 1467671, 4172881, 11913595, 34128769, 98093579, 282770735, 817397180, 2368770203

Offset

1,4

Comments

Column 2 of A209007.

Links

Table of n, a(n) for n=1..25.

Example

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

Crossrefs

Sequence in context: A080522 A173232 A132332 * A240619 A171867 A243513

Adjacent sequences: A208998 A208999 A209000 * A209002 A209003 A209004

Keyword

nonn

Author

R. H. Hardin, Mar 04 2012

Status

approved