A208986 Number of n-bead necklaces labeled with numbers -1..1 not allowing reversal, with sum zero and first differences in -1..1.

1, 1, 1, 2, 3, 5, 9, 18, 35, 73, 151, 324, 691, 1503, 3277, 7212, 15927, 35407, 78967, 176942, 397717, 897079, 2029071, 4602438, 10464647, 23849545, 54468627, 124646180, 285762575, 656268311, 1509570433, 3477615648, 8022765075

Offset

1,4

Comments

Column 1 of A208993.

Links

R. H. Hardin, Table of n, a(n) for n = 1..35

Example

All solutions for n=7:
..0...-1...-1...-1...-1...-1...-1...-1...-1
..0...-1...-1...-1....0....0....0....0....0
..0....0....0....0....0....0....0....1...-1
..0....1....1....0....0....0....1....0....0
..0....1....0....1....1....0....0....0....1
..0....0....1....1....0....1....0....0....1
..0....0....0....0....0....0....0....0....0

Crossrefs

Sequence in context: A056766 A262450 A355190 * A080091 A000602 A034790

Adjacent sequences: A208983 A208984 A208985 * A208987 A208988 A208989

Keyword

nonn

Author

R. H. Hardin, Mar 04 2012

Status

approved