A209024 Number of n-bead necklaces labeled with numbers -n..n allowing reversal, with sum zero and first differences in -n..n.

1, 2, 4, 23, 187, 2798, 52208, 1210780, 32915700, 1029158718, 36366029268, 1434017630862, 62448855324545, 2977529703278272, 154305670613042906, 8637641797383212010, 519466811614545786362, 33406493488132547194879, 2287819864082225737308655, 166242770253180661727941435

Offset

1,2

Links

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

Example

Some solutions for n=6:
.-4...-6...-4...-3...-3...-2...-5...-4...-5...-3...-3...-5...-4...-6...-3...-4
..0...-2...-2...-1...-2....0...-1....0...-3...-1...-2...-5...-3....0...-2....0
.-2....3....3....1....3....1....2...-1....2...-1....4....0....0....0...-1....2
..4....3....4....3...-1...-2....3....5....0....1...-1....6....3....0....0....3
..0....4...-1....0....1....1....2....0....5....4....2....3....4....6....4...-2
..2...-2....0....0....2....2...-1....0....1....0....0....1....0....0....2....1

Crossrefs

Diagonal of A209032.

Sequence in context: A366224 A009313 A009317 * A081680 A269573 A147761

Adjacent sequences: A209021 A209022 A209023 * A209025 A209026 A209027

Keyword

nonn

Author

R. H. Hardin, Mar 04 2012

Extensions

a(12)-a(20) from Andrew Howroyd, Mar 19 2017

Status

approved