A208808 Number of n-bead necklaces labeled with numbers -2..2 not allowing reversal, with sum zero and three times sum of squares <= n*(2)*(2+1).

1, 2, 5, 15, 59, 187, 753, 3125, 12503, 54977, 229533, 1010861, 4476937, 19717931, 89279611, 400928643, 1825710727, 8356818535, 38284519557, 177041554325

Offset

1,2

Comments

Column 2 of A208814.

Links

Table of n, a(n) for n=1..20.

Example

Some solutions for n=6:
.-1...-2...-2...-2...-2...-2...-1...-2...-2...-2...-2...-2...-2...-1...-1...-2
.-1...-1...-1....1....1....2...-1....1....0...-1....0...-1....1...-1...-1...-1
..0....2....1....0....2...-1....2....1....1....1...-1....1....0....1....0....1
..0....1....2....1...-1....0....0....1....0....2....2....1...-1....1....2....0
..1...-1....1...-1....1....1...-1...-1....0...-1....1....2....2...-1...-1....0
..1....1...-1....1...-1....0....1....0....1....1....0...-1....0....1....1....2

Crossrefs

Sequence in context: A348365 A048192 A078792 * A266682 A325575 A332248

Adjacent sequences: A208805 A208806 A208807 * A208809 A208810 A208811

Keyword

nonn

Author

R. H. Hardin, Mar 01 2012

Status

approved