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A235886
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Number of (n+1) X (1+1) 0..3 arrays with the minimum plus the upper median equal to the lower median plus the maximum in every 2 X 2 subblock.
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1
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40, 112, 352, 1216, 4480, 17152, 67072, 265216, 1054720, 4206592, 16801792, 67158016, 268533760, 1073938432, 4295360512, 17180655616, 68721049600, 274881052672, 1099517919232, 4398059094016, 17592211210240, 70368794509312
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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) = 6*a(n-1) - 8*a(n-2).
G.f.: 8*x*(5 - 16*x) / ((1 - 2*x)*(1 - 4*x)).
a(n) = 2^(2+n) * (3+2^n).
(End)
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EXAMPLE
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Some solutions for n=4:
..0..0....1..1....1..1....3..3....3..3....0..2....3..3....3..3....0..0....2..1
..3..3....2..2....3..3....2..2....2..2....0..2....3..3....2..2....1..1....2..1
..2..2....2..2....3..3....0..0....3..3....0..2....3..3....2..2....0..0....1..2
..3..3....1..1....2..2....0..0....3..3....0..2....2..2....1..1....2..2....1..2
..1..1....3..3....2..2....0..0....1..1....2..0....2..2....3..3....2..2....1..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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