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A184145
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1/4 the number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock having at least two equal elements connected horizontally or vertically.
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1
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43, 499, 5695, 65227, 746503, 8544883, 97806031, 1119511003, 12814167895, 146673819139, 1678861073311, 19216616595691, 219957659413927, 2517684199404691, 28817972258232175, 329856907907420923
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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) = 9*a(n-1) + 28*a(n-2).
G.f.: x*(43 + 112*x) / (1 - 9*x - 28*x^2).
a(n) = (2^(-n)*((9-sqrt(193))^n*(-25+2*sqrt(193)) + (9+sqrt(193))^n*(25+2*sqrt(193)))) / sqrt(193).
(End)
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EXAMPLE
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Some solutions for 3 X 2 with a(1,1)=0:
..0..2....0..2....0..0....0..0....0..1....0..0....0..2....0..2....0..0....0..0
..3..2....1..1....2..0....1..1....0..2....0..3....1..1....0..0....1..2....0..0
..0..2....2..3....0..0....1..0....3..2....1..1....3..2....0..3....1..2....0..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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