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A301960
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Number of nX4 0..1 arrays with every element equal to 0, 1 or 4 horizontally or antidiagonally adjacent elements, with upper left element zero.
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1
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5, 9, 25, 64, 169, 441, 1156, 3025, 7921, 20736, 54289, 142129, 372100, 974169, 2550409, 6677056, 17480761, 45765225, 119814916, 313679521, 821223649, 2149991424, 5628750625, 14736260449, 38580030724, 101003831721, 264431464441
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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) = 2*a(n-1) +2*a(n-2) -a(n-3) for n>4
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EXAMPLE
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Some solutions for n=5
..0..0..1..0. .0..1..1..0. .0..0..1..0. .0..1..0..1. .0..1..0..1
..1..1..1..0. .0..0..1..0. .1..1..1..0. .0..1..1..1. .0..1..0..1
..1..0..1..0. .1..0..1..0. .1..0..1..1. .0..1..0..1. .1..0..1..0
..1..0..0..0. .1..0..1..0. .1..0..0..1. .0..0..0..1. .1..0..1..1
..1..0..1..1. .1..0..1..0. .1..1..0..0. .0..1..0..0. .1..0..0..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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