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A209345 Number of 4-bead necklaces labelled with numbers -n..n allowing reversal, with sum zero with no three beads in a row equal 2
4, 15, 35, 72, 128, 205, 311, 448, 618, 829, 1083, 1382, 1734, 2141, 2605, 3134, 3730, 4395, 5137, 5958, 6860, 7851, 8933, 10108, 11384, 12763, 14247, 15844, 17556, 19385, 21339, 23420, 25630, 27977, 30463, 33090, 35866, 38793, 41873, 45114, 48518, 52087 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 4 of A209344

LINKS

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

FORMULA

Empirical: a(n) = 3*a(n-1) -3*a(n-2) +2*a(n-3) -3*a(n-4) +3*a(n-5) -a(n-6)

EXAMPLE

Some solutions for n=10

.-5...-5...-9...-5...-7...-2...-9..-10...-9...-4...-7..-10...-4...-6...-7...-7

..1...-3....5....0....1...-1....5....5...-4....1...-1...-3...-4....1....7...-6

.-3...-2...-5....4....4....4...-6...-3....3....0....6...10....3...-2...-7...10

..7...10....9....1....2...-1...10....8...10....3....2....3....5....7....7....3

CROSSREFS

Sequence in context: A113693 A211537 A213420 * A190093 A077414 A015653

Adjacent sequences:  A209342 A209343 A209344 * A209346 A209347 A209348

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 06 2012

STATUS

approved

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Last modified August 20 11:41 EDT 2017. Contains 290835 sequences.