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A221462
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Number of 0..7 arrays of length n with each element unequal to at least one neighbor, starting with 0
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2
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0, 7, 49, 392, 3087, 24353, 192080, 1515031, 11949777, 94253656, 743424031, 5863743809, 46250174880, 364797430823, 2877333239921, 22694914695208, 179005735545903, 1411904551687777, 11136372010635760, 87837935936264759
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OFFSET
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1,2
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COMMENTS
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Column 7 of A221463
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LINKS
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R. H. Hardin, Table of n, a(n) for n = 1..134
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FORMULA
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Empirical: a(n) = 7*a(n-1) +7*a(n-2)
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EXAMPLE
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Some solutions for n=6
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..6....5....5....7....7....1....7....4....1....3....1....4....2....5....6....1
..1....4....5....3....2....2....4....7....1....5....2....3....5....2....7....2
..1....1....0....4....0....3....6....5....2....1....4....3....1....7....3....5
..4....6....4....4....3....7....1....2....1....1....2....0....0....4....5....1
..2....2....6....7....0....1....2....0....5....2....1....4....6....0....0....0
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CROSSREFS
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Sequence in context: A349781 A199554 A343583 * A090016 A005924 A145358
Adjacent sequences: A221459 A221460 A221461 * A221463 A221464 A221465
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin Jan 17 2013
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STATUS
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approved
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