A208998 Number of 7-bead necklaces labeled with numbers -n..n not allowing reversal, with sum zero and first differences in -n..n.

9, 155, 1111, 4935, 16307, 44209, 104001, 219929, 428031, 779487, 1344353, 2215747, 3514415, 5393753, 8045199, 11704103, 16655941, 23243017, 31871521, 43019059, 57242537, 75186543, 97592047, 125305621, 159288983, 200629037, 250548251

Offset

1,1

Comments

Row 7 of A208993.

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-3) - a(n-4) - 2*a(n-5) - a(n-6) + a(n-8) + a(n-9) + a(n-10) + a(n-12) - a(n-13) - a(n-15) - a(n-16) - a(n-17) + a(n-19) + 2*a(n-20) + a(n-21) - a(n-22) - a(n-23) - a(n-24) + a(n-25).

Example

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

Crossrefs

Sequence in context: A185759 A215557 A365015 * A236578 A305139 A208545

Adjacent sequences: A208995 A208996 A208997 * A208999 A209000 A209001

Keyword

nonn

Author

R. H. Hardin, Mar 04 2012

Status

approved