A208817 Number of n-bead necklaces labeled with numbers -n..n allowing reversal, with sum zero.

1, 3, 8, 75, 905, 17339, 417204, 12322101, 427919519, 17112239947, 774546254686

Offset

1,2

Comments

Diagonal of A208825.

Links

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

Example

All solutions for n=3:
.-2....0...-3...-3...-2...-1...-2...-1
.-1....0....0....1....0...-1....1....0
..3....0....3....2....2....2....1....1

Crossrefs

Sequence in context: A095051 A362990 A092372 * A356529 A060752 A347641

Adjacent sequences: A208814 A208815 A208816 * A208818 A208819 A208820

Keyword

nonn

Author

R. H. Hardin, Mar 01 2012

Status

approved