A209000 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A209000

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

1, 1, 1, 1, 1, 2, 3, 5, 7, 10, 13, 20, 29, 51, 85, 155, 265, 471, 803, 1408, 2437, 4309, 7599, 13590, 24231, 43506, 77953, 140219, 252095, 454761, 820873, 1485835, 2691995, 4887096, 8879875, 16158907, 29429535, 53665336

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,6

COMMENTS

Column 1 of A209007.

LINKS

Table of n, a(n) for n=1..38.

EXAMPLE

All solutions for n=11:

.-1...-1...-1...-1...-1....0...-1...-1...-1...-1...-1...-1...-1

.-1....0...-1....0...-1....0....0....0...-1...-1...-1....0....0

.-1....0....0....0....0....0....0....1....0....0...-1....0....0

..0....0....1....0....0....0....0....1....0....0....0....1....0

..0....0....1....1....1....0....0....0....0....0....1....1....0

..1....0....1....1....1....0....1....0....0....1....1....0....0

..1....0....0....0....1....0....1....0....1....1....1....0....1

..1....1....0....0....0....0....0....0....1....1....1....0....1

..1....1....0....0....0....0....0....0....1....0....0....0....0

..0....0....0....0....0....0....0....0....0....0....0....0....0

CROSSREFS

Sequence in context: A023192 A064480 A274111 * A115024 A167050 A308388

Adjacent sequences: A208997 A208998 A208999 * A209001 A209002 A209003

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 04 2012

STATUS

approved