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A209348
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Number of 7-bead necklaces labelled with numbers -n..n allowing reversal, with sum zero with no three beads in a row equal
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1
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21, 514, 4029, 18646, 62853, 172610, 409199, 870122, 1699831, 3104474, 5365417, 8858142, 14068115, 21614144, 32266607, 46975088, 66888951, 93389664, 128113109, 172986976, 230254897, 302518564, 392763779, 504407780, 641326401, 807907094
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graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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Row 7 of A209344
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LINKS
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R. H. Hardin, Table of n, a(n) for n = 1..210
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FORMULA
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Empirical: a(n) = 3*a(n-1) -2*a(n-2) -a(n-3) +a(n-4) -2*a(n-5) +5*a(n-6) -5*a(n-7) +3*a(n-8) -3*a(n-10) +5*a(n-11) -5*a(n-12) +2*a(n-13) -a(n-14) +a(n-15) +2*a(n-16) -3*a(n-17) +a(n-18)
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EXAMPLE
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Some solutions for n=5
.-5...-4...-4...-5...-5...-4...-4...-3...-2...-2...-4...-4...-5...-5...-5...-4
.-5...-3....0...-4....0...-2...-3...-1...-1...-1...-3...-2...-2...-4...-3....1
.-1....5...-4....2....0...-2....1...-2...-1...-2....4....3...-1....0....5...-3
..5....5....1....2....5....0....1....2....1...-1....1....3....5....4....2...-2
.-4...-3....2....1...-1....2....5....2...-1....3....5...-4....3....2...-2....1
..5...-1....3...-1...-4....1....2....0....3....3...-4....0...-2....1....0....2
..5....1....2....5....5....5...-2....2....1....0....1....4....2....2....3....5
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CROSSREFS
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Sequence in context: A006299 A065921 A129993 * A095655 A221766 A080483
Adjacent sequences: A209345 A209346 A209347 * A209349 A209350 A209351
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin Mar 06 2012
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STATUS
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approved
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