login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A209025 Number of n-bead necklaces labeled with numbers -1..1 allowing reversal, with sum zero and first differences in -1..1. 1
1, 1, 1, 2, 2, 4, 6, 13, 21, 45, 83, 181, 362, 794, 1676, 3703, 8049, 17925, 39679, 88980, 199308, 449714, 1015574, 2303940, 5234731, 11931095, 27239911, 62337821, 142894336, 328168558, 754815704, 1738888333, 4011453913, 9266702091, 21433240903, 49633242760 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..100

EXAMPLE

All solutions for n=6:

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

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

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

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

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

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

CROSSREFS

Column 1 of A209032.

Sequence in context: A188538 A282164 A268175 * A153955 A074028 A181926

Adjacent sequences:  A209022 A209023 A209024 * A209026 A209027 A209028

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 04 2012

EXTENSIONS

a(33)-a(36) from Andrew Howroyd, Mar 19 2017

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 27 15:01 EST 2020. Contains 332306 sequences. (Running on oeis4.)