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A221461
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Number of 0..6 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, 6, 36, 252, 1728, 11880, 81648, 561168, 3856896, 26508384, 182191680, 1252200384, 8606352384, 59151316608, 406546013952, 2794183983360, 19204379983872, 131991383803392, 907174582723584, 6234995799161856
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 6*a(n-1) +6*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....4....2....3....2....4....2....6....3....3....1....2....1....5....5....3
..3....2....5....0....2....5....1....6....2....1....2....4....4....5....0....3
..4....4....4....3....6....3....2....2....0....4....2....0....0....4....0....0
..4....3....6....6....1....5....2....2....5....6....3....4....3....0....5....3
..6....4....4....2....6....0....3....4....3....2....6....2....6....4....1....4
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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