A209076 Number of 7-bead necklaces labeled with numbers -n..n not allowing reversal, with sum zero and avoiding the pattern z z+1 z+2.

39, 1007, 8008, 37108, 125428, 344618, 817594, 1738838, 3397900, 6206228, 10727576, 17711618, 28130798, 43220926, 64524812, 93939228, 133765612, 186763798, 256208998, 345952710, 460486468, 605008920, 785496844, 1008779010

Offset

1,1

Comments

Row 7 of A209073.

Links

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

Formula

Empirical: a(n) = 5*a(n-1) - 11*a(n-2) + 16*a(n-3) - 20*a(n-4) + 22*a(n-5) - 19*a(n-6) + 11*a(n-7) - 11*a(n-9) + 19*a(n-10) - 22*a(n-11) + 20*a(n-12) - 16*a(n-13) + 11*a(n-14) - 5*a(n-15) + a(n-16) for n > 18.

Example

Some solutions for n=6:
  -4  -5  -4  -6  -5  -6  -5  -6  -6  -6  -4  -6  -5  -5  -6  -5
  -4  -1  -4  -1  -4  -5  -2  -4  -1  -5  -3  -3  -5  -1  -4  -5
  -2   2   1   2   1   1   2   0   2   5   4   2   6   6   4  -5
   6   4   5   6   4   6   3   4   5   6   3   5   3   1   5   4
   2  -2   6  -1   3   3   2   5  -4   0  -3   0  -4  -4   1   2
  -2  -3  -4   5   0   2   2  -2   2  -4   0   2   0  -2  -4   6
   4   5   0  -5   1  -1  -2   3   2   4   3   0   5   5   4   3

Crossrefs

Sequence in context: A016091 A028227 A028219 * A251327 A014936 A227524

Adjacent sequences: A209073 A209074 A209075 * A209077 A209078 A209079

Keyword

nonn

Author

R. H. Hardin, Mar 04 2012

Status

approved