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A208771
Number of n-bead necklaces labeled with numbers 1..n not allowing reversal, with no adjacent beads differing by more than 1.
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
1,2
LINKS
EXAMPLE
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
CROSSREFS
Diagonal of A208777.
Sequence in context: A131630 A305652 A356938 * A036884 A102291 A034691
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 01 2012
EXTENSIONS
a(19)-a(28) from Andrew Howroyd, Mar 18 2017
STATUS
approved