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A221599
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Number of 0..n arrays of length 7 with each element differing from at least one neighbor by 1 or less.
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1
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128, 1113, 4240, 11011, 22912, 41401, 67936, 103975, 150976, 210397, 283696, 372331, 477760, 601441, 744832, 909391, 1096576, 1307845, 1544656, 1808467, 2100736, 2422921, 2776480, 3162871, 3583552, 4039981, 4533616, 5065915, 5638336
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 243*n^3 - 351*n^2 + 237*n + 127 for n>2.
G.f.: x*(128 + 601*x + 556*x^2 + 217*x^3 - 16*x^4 - 28*x^5) / (1 - x)^4.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>6.
(End)
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EXAMPLE
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Some solutions for n=6:
..4....5....5....5....5....2....0....0....1....6....4....3....1....4....5....1
..3....4....6....5....6....2....0....1....1....6....3....2....0....5....4....2
..2....4....5....2....5....1....0....1....4....6....0....1....5....3....3....4
..2....1....3....1....4....5....2....4....5....1....1....1....4....2....4....4
..5....2....2....4....5....4....1....4....3....2....6....0....3....4....2....5
..5....5....1....4....2....4....3....6....3....1....5....3....2....4....3....3
..6....5....1....3....1....5....2....5....4....1....5....4....2....3....4....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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