A209031 Number of n-bead necklaces labeled with numbers -7..7 allowing reversal, with sum zero and first differences in -7..7.

1, 4, 12, 88, 625, 5648, 52208, 505857, 4992048, 50169067, 510807173, 5260218485, 54684221779, 573168585795, 6050541798221, 64271927631233, 686512535921878, 7369066749454264, 79449368494683376, 859987831858141180, 9342319735394175920, 101820772577694786504

Offset

1,2

Links

Andrew Howroyd, Table of n, a(n) for n = 1..50

Example

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

Crossrefs

Column 7 of A209032.

Sequence in context: A194004 A064280 A203379 * A096424 A009629 A203110

Adjacent sequences: A209028 A209029 A209030 * A209032 A209033 A209034

Keyword

nonn

Author

R. H. Hardin, Mar 04 2012

Extensions

a(14)-a(22) from Andrew Howroyd, Mar 12 2017

Status

approved