A208726 Number of 2n-bead necklaces labeled with numbers 1..7 not allowing reversal, with neighbors differing by exactly 1.

6, 11, 20, 45, 104, 290, 796, 2366, 7076, 21684, 66996, 209594, 659560, 2090590, 6659120, 21312716, 68476512, 220798322, 714144612, 2316303916, 7531662344, 24545750474, 80160395804, 262280793024, 859662037240, 2822180991508, 9278652591844, 30547892144882

Offset

1,1

Links

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

Example

All solutions for n=2:
..5....1....2....3....5....4....2....4....6....1....3
..6....2....3....4....6....5....3....5....7....2....4
..5....1....2....5....7....4....4....6....6....3....3
..6....2....3....4....6....5....3....5....7....2....4

Crossrefs

Column 7 of A208727.

Sequence in context: A021011 A000382 A208670 * A192750 A000383 A205540

Adjacent sequences: A208723 A208724 A208725 * A208727 A208728 A208729

Keyword

nonn

Author

R. H. Hardin, Mar 01 2012

Extensions

a(13)-a(28) from Andrew Howroyd, Mar 18 2017

Status

approved