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A208718 Number of n-bead necklaces labeled with numbers 1..5 allowing reversal, with no adjacent beads differing by more than 1. 1
5, 9, 13, 24, 38, 78, 140, 306, 634, 1464, 3326, 8066, 19454, 48534, 121294, 308154, 785222, 2018548, 5203634, 13482426, 35019010, 91251438, 238278314, 623629333, 1635062126, 4294493670, 11296419934, 29757590061, 78489973742, 207281830814 (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(2n+1) = (1/2) * (A208774(2n+1) + r(n+1)) where r(n) = A057960(n+1). - Andrew Howroyd, Mar 03 2017

a(2n) = (1/2) * A208774(2n) + (1/4) * (r(n) + r(n+1)) where r(n) = A057960(n+1). - Andrew Howroyd, Mar 03 2017

EXAMPLE

All solutions for n=3:

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

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

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

CROSSREFS

Column 5 of A208721.

Cf. A208774, A057960.

Sequence in context: A314796 A314797 A314798 * A208774 A271391 A151907

Adjacent sequences:  A208715 A208716 A208717 * A208719 A208720 A208721

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 01 2012

EXTENSIONS

a(25)-a(30) from Andrew Howroyd, Mar 03 2017

STATUS

approved

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Last modified April 8 14:52 EDT 2020. Contains 333314 sequences. (Running on oeis4.)