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A209488 Number of 7-bead necklaces labeled with numbers -n..n allowing reversal, with sum zero and avoiding the patterns z z+1 z+2 and z z-1 z-2. 1
15, 458, 3740, 17771, 60778, 168453, 401634, 857433, 1679810, 3074315, 5321674, 8796771, 13984178, 21501971, 32119660, 46785813, 66648788, 93089119, 127741326, 172532039, 229703658, 301856427, 391974770, 503474661, 640230118, 806627193 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 7 of A209485.

LINKS

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

FORMULA

Empirical: a(n) = 2*a(n-1) - a(n-3) - a(n-5) + a(n-6) - 2*a(n-7) + 2*a(n-8) + a(n-9) - a(n-13) - 2*a(n-14) + 2*a(n-15) - a(n-16) + a(n-17) + a(n-19) - 2*a(n-21) + a(n-22) for n > 24.

EXAMPLE

Some solutions for n=5:

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

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

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

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

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

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

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

CROSSREFS

Sequence in context: A036506 A306675 A219561 * A320097 A177080 A306609

Adjacent sequences:  A209485 A209486 A209487 * A209489 A209490 A209491

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 09 2012

STATUS

approved

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Last modified October 28 01:29 EDT 2021. Contains 348305 sequences. (Running on oeis4.)