A208823 Number of n-bead necklaces labeled with numbers -6..6 allowing reversal, with sum zero.

1, 7, 25, 210, 1755, 17339, 177097, 1888153, 20587627, 228891069, 2582512649, 29499246456

Offset: 1

Author

R. H. Hardin, Mar 01 2012

Keywords

• nonn

Comments

Column 6 of A208825.

Examples

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