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A251229
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Number of (n+1) X (1+1) 0..3 arrays with every 2 X 2 subblock summing to 6 and no 2 X 2 subblock having exactly two nonzero entries.
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1
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38, 110, 322, 966, 2930, 8982, 27714, 85958, 267602, 835574, 2615266, 8202150, 25769714, 81093846, 255569538, 806554502, 2548769426, 8064427958, 25546995490, 81022985574, 257251995698, 817658450070, 2601529209282, 8285338752326
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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) = 7*a(n-1) - 12*a(n-2) - 8*a(n-3) + 24*a(n-4).
Empirical g.f.: 2*x*(19 - 78*x + 4*x^2 + 168*x^3) / ((1 - 2*x)*(1 - 3*x)*(1 - 2*x - 4*x^2)). - Colin Barker, Nov 27 2018
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EXAMPLE
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Some solutions for n=4:
..2..1....1..2....1..3....2..1....2..1....0..2....2..1....3..1....3..2....1..1
..3..0....3..0....1..1....1..2....1..2....1..3....3..0....0..2....1..0....2..2
..2..1....1..2....2..2....2..1....0..3....2..0....1..2....1..3....3..2....0..2
..1..2....1..2....1..1....2..1....1..2....3..1....0..3....1..1....0..1....3..1
..2..1....3..0....1..3....3..0....0..3....0..2....2..1....1..3....2..3....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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