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

Author

R. H. Hardin, Mar 01 2012

Keywords

• nonn

Examples

			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
		

Links

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

Crossrefs

Diagonal of A208721.

Extensions

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