A208966 Number of n-bead necklaces labeled with numbers -4..4 allowing reversal, with sum zero and first and second differences in -4..4.

1, 2, 2, 8, 19, 90, 371, 1755, 8092, 37970, 179133, 857902, 4152036, 20313811, 100217735, 497983883, 2488970462, 12503041095, 63083893996, 319545209584, 1624399382535, 8284482761844, 42377064630483, 217362286106711, 1117715413419540, 5760869940768290

Offset

1,2

Links

Andrew Howroyd, Table of n, a(n) for n = 1..50

Example

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

Crossrefs

Column 4 of A208970.

Sequence in context: A175395 A169888 A168506 * A067640 A098277 A242658

Adjacent sequences: A208963 A208964 A208965 * A208967 A208968 A208969

Keyword

nonn

Author

R. H. Hardin, Mar 03 2012

Extensions

a(16)-a(26) from Andrew Howroyd, Mar 12 2017

Status

approved