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A251145
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Number of (n+1) X (4+1) 0..2 arrays with every 2 X 2 subblock summing to 4 and no 2 X 2 subblock having exactly two nonzero entries.
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1
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107, 161, 247, 401, 667, 1141, 1987, 3521, 6327, 11521, 21227, 39541, 74387, 141201, 270167, 520561, 1009147, 1966581, 3849507, 7563681, 14908407, 29462561, 58351947, 115776501, 230052467, 457677041, 911425687, 1816495121, 3622705627
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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-1) - 5*a(n-3) + a(n-4) + 2*a(n-5).
Empirical g.f.: x*(107 - 160*x - 236*x^2 + 195*x^3 + 162*x^4) / ((1 - x)*(1 + x)*(1 - 2*x)*(1 - x - x^2)). - Colin Barker, Nov 26 2018
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EXAMPLE
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Some solutions for n=4:
..0..1..0..1..0....1..2..0..2..0....0..2..1..2..0....0..2..0..2..0
..1..2..1..2..1....0..1..1..1..1....1..1..0..1..1....1..1..1..1..1
..0..1..0..1..0....1..2..0..2..0....1..1..2..1..1....1..1..1..1..1
..1..2..1..2..1....0..1..1..1..1....1..1..0..1..1....0..2..0..2..0
..0..1..0..1..0....2..1..1..1..1....1..1..2..1..1....1..1..1..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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