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A238768
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Number of n X 1 0..3 arrays with no element equal to the sum modulo 4 of elements to its left or elements above it.
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3
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3, 6, 14, 32, 72, 164, 372, 844, 1916, 4348, 9868, 22396, 50828, 115356, 261804, 594172, 1348492, 3060444, 6945772, 15763644, 35776076, 81194908, 184274348, 418216316, 949154828, 2154136156, 4888878444, 11095460412, 25181489612
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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) = a(n-1) + 2*a(n-2) + 2*a(n-3).
Empirical g.f.: x*(3 + 3*x + 2*x^2) / (1 - x - 2*x^2 - 2*x^3). - Colin Barker, Feb 24 2018
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EXAMPLE
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Some solutions for n=5:
..3....3....2....1....1....2....1....3....2....1....3....3....1....1....2....1
..1....1....3....2....2....3....3....2....3....3....1....2....2....2....1....3
..2....2....3....1....2....3....1....2....2....3....2....3....2....2....2....2
..1....3....1....3....3....3....2....2....2....2....1....1....3....2....2....1
..1....3....3....2....1....1....2....2....2....2....2....2....3....1....2....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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