A208962 Number of n-bead necklaces labeled with numbers -n..n allowing reversal, with sum zero and first and second differences in -n..n.

1, 1, 2, 8, 40, 495, 7425, 140429, 3014206, 73238115, 2000005946

Offset

1,3

Comments

Diagonal of A208970.

Links

Table of n, a(n) for n=1..11.

Example

Some solutions for n=5:
.-2...-3...-3...-1...-2...-1...-1...-2...-2...-1...-2....0...-2...-2...-3...-3
.-2...-3...-1....0...-1....0...-1...-1....0....0...-1....0....0....0...-2...-3
..1....2....1...-1....2....0....1....2....2...-1....1....0....0....1....3....1
..1....2....3....0....0....0....0....1...-1....1....2....0....1....0....3....3
..2....2....0....2....1....1....1....0....1....1....0....0....1....1...-1....2

Crossrefs

Sequence in context: A111394 A140363 A280921 * A351109 A012597 A012534

Adjacent sequences: A208959 A208960 A208961 * A208963 A208964 A208965

Keyword

nonn

Author

R. H. Hardin, Mar 03 2012

Status

approved