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A183324
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Number of nX3 binary arrays with each 1 adjacent to exactly two other 1s
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2
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1, 3, 6, 10, 19, 37, 69, 129, 244, 460, 865, 1629, 3069, 5779, 10882, 20494, 38595, 72681, 136873, 257761, 485416, 914136, 1721505, 3241945, 6105241, 11497411, 21651966, 40775058, 76787731, 144606925, 272324269, 512842017, 965785884
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OFFSET
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1,2
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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)-a(n-2)+2*a(n-3)-a(n-4).
Empirical: G.f. -x*(-1-x+x^3-x^2) / ( 1-2*x+x^2-2*x^3+x^4 ), see A033305 - R. J. Mathar, Sep 27 2013
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EXAMPLE
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All solutions for 4X3
..0..0..0....0..0..0....1..1..1....0..0..0....0..0..0....0..0..0....1..1..0
..0..0..0....0..0..0....1..0..1....1..1..1....0..1..1....1..1..0....1..1..0
..1..1..0....0..0..0....1..0..1....1..0..1....0..1..1....1..1..0....0..0..0
..1..1..0....0..0..0....1..1..1....1..1..1....0..0..0....0..0..0....0..0..0
...
..0..0..0....0..1..1....1..1..1
..0..0..0....0..1..1....1..0..1
..0..1..1....0..0..0....1..1..1
..0..1..1....0..0..0....0..0..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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