A209035 Number of 7-bead necklaces labeled with numbers -n..n allowing reversal, with sum zero and first differences in -n..n.

6, 86, 576, 2517, 8235, 22249, 52208, 110285, 214440, 390344, 672932, 1108883, 1758433, 2698447, 4024458, 5854361, 8330650, 11624758, 15939472, 21513945, 28626249, 37599103, 48802532, 62660333, 79652814, 100324030, 125284570

Offset: 1

Author

R. H. Hardin, Mar 04 2012

Keywords

• nonn

Comments

Row 7 of A209032.

Examples

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

Links

• R. H. Hardin, Table of n, a(n) for n = 1..144

Formula

Empirical: a(n) = a(n-1) + a(n-2) - a(n-5) - a(n-7) - a(n-8) + a(n-10) + a(n-11) + 2*a(n-12) - 2*a(n-16) - a(n-17) - a(n-18) + a(n-20) + a(n-21) + a(n-23) - a(n-26) - a(n-27) + a(n-28).