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 A208668 Number of 2n-bead necklaces labeled with numbers 1..5 allowing reversal, with neighbors differing by exactly 1. 1
 4, 7, 12, 23, 44, 97, 212, 512, 1260, 3251, 8540, 23035, 62780, 173453, 482692, 1353077, 3811364, 10785235, 30625196, 87239999, 249174236, 713416601, 2046945140, 5884580074, 16946835092, 48883925867, 141217957620, 408519816611, 1183291934300, 3431535849813 (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) = (2*A208724(n) + A090993(n))/4. - Andrew Howroyd, Mar 19 2017 EXAMPLE All solutions for n=3: ..3....3....1....1....1....2....2....3....1....2....2....4 ..4....4....2....2....2....3....3....4....2....3....3....5 ..5....3....1....1....3....2....4....3....3....2....4....4 ..4....4....2....2....2....3....5....4....4....3....3....5 ..5....5....3....1....3....2....4....3....3....4....4....4 ..4....4....2....2....2....3....3....4....2....3....3....5 CROSSREFS Column 5 of A208671. Sequence in context: A187211 A023624 A123194 * A243860 A322619 A299900 Adjacent sequences:  A208665 A208666 A208667 * A208669 A208670 A208671 KEYWORD nonn AUTHOR R. H. Hardin, Feb 29 2012 EXTENSIONS a(13)-a(30) from Andrew Howroyd, Mar 19 2017 STATUS approved

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Last modified June 20 01:09 EDT 2021. Contains 345154 sequences. (Running on oeis4.)