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A208717 Number of n-bead necklaces labeled with numbers 1..4 allowing reversal, with no adjacent beads differing by more than 1. 1
4, 7, 10, 18, 28, 56, 98, 208, 418, 933, 2044, 4777, 11072, 26548, 63672, 155248, 379348, 935278, 2311294, 5741228, 14292966, 35699049, 89339860, 224097602, 563074848, 1417313897, 3572747650, 9019154944, 22797181996, 57693378135, 146168107034, 370712004868 (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) * (A208773(2n+1) + A126358(n+1)). - Andrew Howroyd, Mar 03 2017

a(2n) = (1/2) * A208773(2n) + (1/4) * (A126358(n) + A126358(n+1)). - Andrew Howroyd, Mar 03 2017

EXAMPLE

All solutions for n=3:

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

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

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

CROSSREFS

Column 4 of A208721.

Cf. A208773, A126358.

Sequence in context: A310718 A310719 A103408 * A208773 A088408 A027752

Adjacent sequences:  A208714 A208715 A208716 * A208718 A208719 A208720

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 01 2012

EXTENSIONS

a(29)-a(32) from Andrew Howroyd, Mar 03 2017

STATUS

approved

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Last modified January 21 00:11 EST 2022. Contains 350473 sequences. (Running on oeis4.)