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A243601
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Number of length n+2 0..4 arrays with no three elements in a row with pattern aba (with a!=b) and new values 0..4 introduced in 0..4 order.
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1
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4, 10, 29, 96, 349, 1350, 5425, 22297, 92841, 389456, 1640630, 6927937, 29294645, 123967625, 524830618, 2222483751, 9412820990, 39869076285, 168877805414, 715352976032, 3030223762722, 12836088840031, 54374194848619
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = 8*a(n-1) - 18*a(n-2) + 5*a(n-3) + 17*a(n-4) - 4*a(n-5) - 6*a(n-6) - a(n-7).
Empirical g.f.: x*(4 - 22*x + 21*x^2 + 24*x^3 - 15*x^4 - 13*x^5 - 2*x^6) / ((1 - x)*(1 - x - x^2)*(1 - 2*x - x^2)*(1 - 4*x - x^2)). - Colin Barker, Nov 02 2018
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EXAMPLE
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Some solutions for n=5:
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..1....1....0....1....1....1....1....1....1....1....1....1....1....1....1....1
..1....2....1....2....2....1....1....2....1....2....2....2....2....2....2....2
..1....3....1....3....3....2....2....0....0....3....3....3....3....3....3....2
..2....1....0....3....1....2....3....3....2....1....1....1....0....3....0....3
..3....2....2....0....2....1....0....3....3....1....4....4....0....3....1....3
..1....3....2....2....4....3....2....3....4....1....2....4....2....4....3....2
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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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