A208949 Number of 7-bead necklaces labeled with numbers -n..n not allowing reversal, with sum zero with no three beads in a row equal.

38, 988, 7974, 37044, 125322, 344456, 817362, 1738516, 3397474, 6205668, 10726862, 17710724, 28129694, 43219580, 64523202, 93937312, 133763354, 186761160, 256205942, 345949192, 460482450, 605004348, 785491674, 1008773192, 1282606758

Offset

1,1

Comments

Row 7 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) - 9*a(n-6) + 9*a(n-8) - 11*a(n-9) + 10*a(n-10) - 11*a(n-11) + 10*a(n-12) - 5*a(n-13) + a(n-14).

Example

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

Crossrefs

Sequence in context: A028218 A028199 A285236 * A255496 A098612 A268739

Adjacent sequences: A208946 A208947 A208948 * A208950 A208951 A208952

Keyword

nonn

Author

R. H. Hardin, Mar 03 2012

Status

approved