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A209008 Number of 4-bead necklaces labelled with numbers -n..n not allowing reversal, with sum zero and first and second differences in -n..n 1
1, 3, 5, 10, 16, 26, 38, 55, 75, 101, 131, 168, 210, 260, 316, 381, 453, 535, 625, 726, 836, 958, 1090, 1235, 1391, 1561, 1743, 1940, 2150, 2376, 2616, 2873, 3145, 3435, 3741, 4066, 4408, 4770, 5150, 5551, 5971, 6413, 6875, 7360, 7866, 8396, 8948, 9525, 10125 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 4 of A209007

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 3*a(n-1) -2*a(n-2) -2*a(n-3) +3*a(n-4) -a(n-5)

EXAMPLE

Some solutions for n=6

.-2....0...-3...-3...-1...-3...-2...-3...-2...-3...-1...-2...-1...-2...-1...-2

.-2....0....0...-2....1...-3....1...-1...-1....1...-1....1....0....0....0....2

..2....0....3....3...-1....3....0....3....2....3....1....1...-1....0....0....0

..2....0....0....2....1....3....1....1....1...-1....1....0....2....2....1....0

CROSSREFS

Sequence in context: A287563 A184800 A267151 * A032279 A070558 A233758

Adjacent sequences:  A209005 A209006 A209007 * A209009 A209010 A209011

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 04 2012

STATUS

approved

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Last modified August 24 04:58 EDT 2017. Contains 291052 sequences.