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A183980
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1/4 the number of (n+1) X 4 binary arrays with all 2 X 2 subblock sums the same.
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1
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9, 11, 14, 20, 30, 50, 86, 158, 294, 566, 1094, 2150, 4230, 8390, 16646, 33158, 66054, 131846, 263174, 525830, 1050630, 2100230, 4198406, 8394758, 16785414, 33566726, 67125254, 134242310, 268468230, 536920070, 1073807366, 2147581958, 4295098374
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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)=3*a(n-1)-6*a(n-3)+4*a(n-4).
G.f.: x*(9 - 16*x - 19*x^2 + 32*x^3) / ((1 - x)*(1 - 2*x)*(1 - 2*x^2)).
a(n) = (3*2^(n/2) + 2^n + 12) / 2 for n even.
a(n) = 2^((n-5)/2+3) + 2^(n-1) + 6 for n odd.
(End)
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EXAMPLE
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Some solutions for 5 X 4.
..0..1..0..1....1..1..1..1....0..0..1..1....1..0..1..0....1..1..1..0
..1..1..1..1....0..0..0..0....1..1..0..0....1..1..1..1....0..0..0..1
..1..0..1..0....1..1..1..1....0..0..1..1....1..0..1..0....1..1..1..0
..1..1..1..1....0..0..0..0....1..1..0..0....1..1..1..1....0..0..0..1
..0..1..0..1....1..1..1..1....0..0..1..1....0..1..0..1....1..1..1..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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