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A237631
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Number of (n+1) X (2+1) 0..2 arrays with the upper median of every 2 X 2 subblock differing from its horizontal and vertical neighbors by exactly one.
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1
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260, 636, 1220, 2356, 4500, 8594, 16448, 31672, 60362, 116180, 223768, 429680, 822032, 1584164, 3047968, 5848520, 11216480, 21603248, 41526472, 79692176, 153032384, 294531296, 565871200, 1086330032, 2087379872, 4014989408
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = 3*a(n-3) + 10*a(n-4) - 12*a(n-7) - 6*a(n-8) for n>12.
Empirical g.f.: 2*x*(130 + 318*x + 610*x^2 + 788*x^3 - 4*x^4 - 713*x^5 - 1410*x^6 - 1134*x^7 - 614*x^8 - 324*x^9 - 68*x^10 + 5*x^11) / (1 - 3*x^3 - 10*x^4 + 12*x^7 + 6*x^8). - Colin Barker, Oct 24 2018
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EXAMPLE
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Some solutions for n=5:
..2..1..1....1..1..2....0..1..0....2..0..1....2..2..1....0..1..1....0..1..2
..0..2..1....0..2..1....2..0..0....2..1..0....1..0..0....0..0..2....1..2..1
..0..1..2....2..1..0....2..1..2....0..0..0....2..1..0....1..2..1....2..0..0
..0..0..0....0..0..0....0..0..2....0..1..2....1..2..0....2..1..0....1..0..1
..2..1..0....0..1..2....1..0..1....1..2..1....0..1..2....0..0..0....0..0..2
..2..0..2....0..2..1....1..2..2....2..1..1....0..0..0....0..1..2....1..2..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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