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A278151
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Number of n X 2 0..1 arrays with every element both equal and not equal to some elements at offset (-1,-1) (-1,0) (-1,1) (0,-1) (0,1) (1,-1) or (1,0), with upper left element zero.
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1
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0, 2, 7, 22, 75, 254, 859, 2906, 9831, 33258, 112511, 380622, 1287635, 4356038, 14736371, 49852786, 168650767, 570541458, 1930127927, 6529576006, 22089397403, 74727896142, 252802661835, 855225279050, 2893206395127, 9787647126266
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OFFSET
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1,2
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LINKS
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FORMULA
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Empirical: a(n) = 3*a(n-1) + a(n-2) + a(n-3) for n>4.
Empirical g.f.: x^2*(2 - x)*(1 + x) / (1 - 3*x - x^2 - x^3). - Colin Barker, Feb 07 2019
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EXAMPLE
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Some solutions for n=4:
..0..1. .0..0. .0..0. .0..0. .0..0. .0..1. .0..1. .0..0. .0..0. .0..1
..0..1. .1..1. .1..1. .1..0. .1..1. .0..1. .0..1. .1..1. .1..1. .0..1
..1..0. .1..0. .1..0. .1..1. .0..1. .0..1. .1..0. .0..0. .1..0. .0..0
..0..1. .0..1. .0..0. .0..0. .0..0. .1..0. .1..0. .1..1. .1..0. .1..1
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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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