A208771 Number of n-bead necklaces labeled with numbers 1..n not allowing reversal, with no adjacent beads differing by more than 1.

1, 3, 7, 18, 41, 117, 299, 861, 2413, 6955, 19943, 57974, 168013, 489789, 1428611, 4177232, 12226997, 35847123, 105200351, 309086838, 908931221, 2675276801, 7880255915, 23228969891, 68518137777, 202231890207, 597228362551, 1764663912122

Offset: 1

Author

R. H. Hardin, Mar 01 2012

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Diagonal of A208777.

Extensions

a(19)-a(28) from Andrew Howroyd, Mar 18 2017