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A208725 Number of 2n-bead necklaces labeled with numbers 1..6 not allowing reversal, with neighbors differing by exactly 1. 2
5, 9, 16, 35, 78, 210, 551, 1569, 4475, 13078, 38465, 114584, 343026, 1034471, 3134135, 9540969, 29154478, 89407073, 275016292, 848329872, 2623322133, 8130714643, 25252366057, 78577560856, 244933963301, 764707458720, 2391026407058, 7486342546939 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

a(n) = (1/n) * Sum_{d | n} totient(n/d) * A198636(d). - Andrew Howroyd, Mar 18 2017

EXAMPLE

All solutions for n=3:

..3....2....1....3....5....2....4....1....2....3....4....4....1....2....1....3

..4....3....2....4....6....3....5....2....3....4....5....5....2....3....2....4

..5....4....3....5....5....2....6....1....4....3....4....4....3....2....1....3

..4....3....4....6....6....3....5....2....5....4....5....5....2....3....2....4

..5....4....3....5....5....2....6....1....4....5....4....6....3....4....3....3

..4....3....2....4....6....3....5....2....3....4....5....5....2....3....2....4

CROSSREFS

Column 6 of A208727.

Sequence in context: A208669 A062777 A215331 * A272742 A273534 A273115

Adjacent sequences:  A208722 A208723 A208724 * A208726 A208727 A208728

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 01 2012

EXTENSIONS

a(17)-a(28) from Andrew Howroyd, Mar 18 2017

STATUS

approved

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Last modified November 21 06:00 EST 2019. Contains 329350 sequences. (Running on oeis4.)