A208992 Number of n-bead necklaces labeled with numbers -7..7 not allowing reversal, with sum zero and first differences in -7..7.

1, 4, 19, 144, 1207, 11010, 104001, 1008880, 9979817, 100308712, 1021569027, 10520123630, 109367955653

Offset

1,2

Comments

Column 7 of A208993.

Links

Table of n, a(n) for n=1..13.

Example

Some solutions for n=6:
.-4...-6...-3...-7...-6...-3...-3...-5...-7...-4...-5...-2...-6...-4...-5...-7
.-1...-2....0....0....1....0....4....1...-2....3....0....3....1....2...-2...-2
..0....3....0....4....6...-2...-2....1....0....2....4...-1....5...-1...-2....5
..3....1...-2....4....3....4...-2...-1....6....3...-1....0...-2....2....4...-1
.-1....5....5...-1...-1....2....3....2....5...-3....2....1....3....3....5....5
..3...-1....0....0...-3...-1....0....2...-2...-1....0...-1...-1...-2....0....0

Crossrefs

Sequence in context: A197920 A208811 A305725 * A321388 A212717 A067577

Adjacent sequences: A208989 A208990 A208991 * A208993 A208994 A208995

Keyword

nonn

Author

R. H. Hardin, Mar 04 2012

Status

approved