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A184096
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Half the number of n X n toroidal binary arrays with each element having the sum of its vertical neighbors equal to the sum of its horizontal neighbors
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0
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1, 2, 7, 18, 31, 98, 127, 450, 511, 1922, 2047, 7938, 8191, 32258, 32767, 130050, 131071, 522242, 524287, 2093058
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OFFSET
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1,2
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COMMENTS
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Half the number of solutions in 0..1 of a 1-d velocity-one wave equation utt=uxx on a periodic grid
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LINKS
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FORMULA
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Empirical G.f.: x*(1+2*x-2*x^2)*(1+2*x^2)/(1-x)/(1+x)/(1-2*x)/(1+2*x)/(1-2*x^2). [Colin Barker, Feb 17 2012]
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EXAMPLE
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Some solutions for 5X5
..1..0..0..1..1....1..0..0..0..1....1..0..0..0..0....1..1..1..0..0
..0..0..1..1..1....1..1..0..0..0....0..1..0..0..0....0..1..1..1..0
..0..1..1..1..0....0..1..1..0..0....0..0..1..0..0....0..0..1..1..1
..1..1..1..0..0....0..0..1..1..0....0..0..0..1..0....1..0..0..1..1
..1..1..0..0..1....0..0..0..1..1....0..0..0..0..1....1..1..0..0..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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