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A208948 Number of 6-bead necklaces labeled with numbers -n..n not allowing reversal, with sum zero with no three beads in a row equal. 1
20, 264, 1464, 5238, 14430, 33468, 68722, 128844, 225126, 371858, 586668, 890880, 1309872, 1873416, 2616036, 3577366, 4802490, 6342300, 8253854, 10600716, 13453314, 16889298, 20993880, 25860192, 31589644, 38292264, 46087056, 55102358 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 6 of A208945.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 5*a(n-1) - 10*a(n-2) + 11*a(n-3) - 10*a(n-4) + 11*a(n-5) - 10*a(n-6) + 5*a(n-7) - a(n-8).

Empirical g.f.: 2*x*(10 + 82*x + 172*x^2 + 169*x^3 + 88*x^4 + 7*x^5) / ((1 - x)^6*(1 + x + x^2)). - Colin Barker, Jul 07 2018

EXAMPLE

Some solutions for n=5:

  -3  -4  -5  -2  -4  -2  -5  -4  -5  -5  -5  -4  -5  -3  -5  -4

  -1   4  -2  -1  -1   0  -2   1  -1   5  -4  -3   0   5   2   2

  -2   0   0  -2   0   2  -3   2   3   1   3   3   3  -2   3   0

   2  -1   0   3   4   1   3  -2  -5   2   1   1  -3  -2   5  -4

   1   3   3   3  -1   0   3   4   3  -4   1   1   4  -1  -3   4

   3  -2   4  -1   2  -1   4  -1   5   1   4   2   1   3  -2   2

CROSSREFS

Cf. A208945.

Sequence in context: A022111 A025943 A025961 * A278408 A229562 A021854

Adjacent sequences:  A208945 A208946 A208947 * A208949 A208950 A208951

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 03 2012

STATUS

approved

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Last modified December 9 02:15 EST 2021. Contains 349624 sequences. (Running on oeis4.)