A208715 Number of n-bead necklaces labeled with numbers 1..n allowing reversal, with no adjacent beads differing by more than 1.

1, 3, 7, 18, 38, 100, 224, 600, 1498, 4124, 11054, 31347, 87887, 253251, 727867, 2117551, 6159994, 18022052, 52757222, 154874172, 454989753, 1338737083, 3941860229, 11618101775, 34264747423, 101127761931, 298632667837, 882370316215, 2608423280534, 7714578529582

Offset

1,2

Links

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

Example

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

Crossrefs

Diagonal of A208721.

Sequence in context: A006124 A197182 A074587 * A302408 A076700 A265007

Adjacent sequences: A208712 A208713 A208714 * A208716 A208717 A208718

Keyword

nonn

Author

R. H. Hardin, Mar 01 2012

Extensions

a(17)-a(30) from Andrew Howroyd, Mar 03 2017

Status

approved