A209035 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Row 7 of A209032.

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).

EXAMPLE

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

CROSSREFS

Sequence in context: A187740 A332407 A358297 * A230782 A318042 A155654

Adjacent sequences: A209032 A209033 A209034 * A209036 A209037 A209038

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 04 2012

STATUS

approved