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A208669
Number of 2n-bead necklaces labeled with numbers 1..6 allowing reversal, with neighbors differing by exactly 1.
1
5, 9, 16, 32, 65, 152, 360, 937, 2512, 7034, 20124, 58899, 174408, 522453, 1576468, 4787425, 14607763, 44758541, 137607258, 424343533, 1311982883, 4065937220, 12627227963, 39290663343, 122470374536, 382359843141, 1195524220166, 3743191124783
OFFSET
1,1
LINKS
FORMULA
a(n) = (2*A208725(n) + A090995(n))/4.
EXAMPLE
All solutions for n=3:
..3....5....2....3....3....2....4....4....2....1....1....2....1....3....4....1
..4....6....3....4....4....3....5....5....3....2....2....3....2....4....5....2
..5....5....2....3....3....4....4....4....4....1....3....2....3....5....6....1
..6....6....3....4....4....3....5....5....5....2....4....3....2....4....5....2
..5....5....4....5....3....4....6....4....4....1....3....2....3....5....6....3
..4....6....3....4....4....3....5....5....3....2....2....3....2....4....5....2
CROSSREFS
Column 6 of A208671.
Sequence in context: A088495 A352665 A218611 * A062777 A215331 A208725
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 29 2012
EXTENSIONS
a(16)-a(28) from Andrew Howroyd, Mar 19 2017
STATUS
approved