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A196596
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Number of n X 3 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 1,2,4,0,3 for x=0,1,2,3,4.
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2
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1, 3, 16, 37, 116, 356, 1068, 3217, 9717, 29312, 88421, 266766, 804810, 2428010, 7325047, 22098889, 66669946, 201136011, 606805618, 1830666938, 5522924202, 16662065199, 50267649223, 151652062770, 457517876847, 1380281967900
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OFFSET
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1,2
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COMMENTS
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Every 0 is next to 0 1's, every 1 is next to 1 2's, every 2 is next to 2 4's, every 3 is next to 3 0's, every 4 is next to 4 3's.
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LINKS
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FORMULA
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Empirical: a(n) = 2*a(n-1) + 2*a(n-2) + 3*a(n-3) + a(n-4) - a(n-5).
Empirical g.f.: x*(1 + x + 8*x^2 - 4*x^3) / (1 - 2*x - 2*x^2 - 3*x^3 - x^4 + x^5). - Colin Barker, Mar 01 2018
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EXAMPLE
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Some solutions for n=4:
..0..0..0....0..3..0....0..0..0....0..0..0....0..3..0....0..3..0....0..3..0
..0..0..0....0..0..3....0..0..3....3..0..3....0..0..3....0..0..0....0..0..0
..3..0..0....0..0..0....3..0..0....0..0..0....3..0..0....0..0..3....3..0..3
..0..0..0....0..3..0....0..0..0....0..3..0....0..0..0....0..3..0....0..3..0
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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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