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A204078
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Number of nX2 0..3 arrays with every element neighboring horizontally or vertically both a 0 and a 1.
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1
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0, 4, 4, 16, 100, 324, 1296, 5476, 21316, 85264, 343396, 1368900, 5475600, 21921124, 87647044, 350588176, 1402502500, 5609710404, 22438841616, 89756564836, 359023862596, 1436095450384, 5744391388516, 22977546380100, 91910185520400
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OFFSET
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1,2
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COMMENTS
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Column 2 of A204084.
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LINKS
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R. H. Hardin, Table of n, a(n) for n = 1..210
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FORMULA
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Empirical: a(n) = 2*a(n-1) +4*a(n-2) +17*a(n-3) -2*a(n-4) -4*a(n-5) -16*a(n-6)
Empirical: a(n) = 4*round(2^n/7)^2 - Mark van Hoeij, May 14 2013
Empirical g.f.: 4*x^2*(1 - x - 2*x^2 - 4*x^3) / ((1 - x)*(1 - 4*x)*(1 + x + x^2)*(1 + 2*x + 4*x^2)). - Colin Barker, Jun 06 2018
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EXAMPLE
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Some solutions for n=5:
..0..1....0..0....1..0....1..1....0..0....1..0....0..0....1..0....1..0....0..0
..0..1....1..1....1..0....0..0....1..1....1..0....1..1....1..0....1..0....1..1
..2..1....2..2....0..3....1..0....1..1....1..0....1..1....1..0....3..3....0..2
..1..0....0..0....0..1....1..0....0..0....0..0....0..0....0..0....0..1....0..0
..1..0....1..1....0..1....1..0....1..1....1..1....1..1....1..1....0..1....1..1
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CROSSREFS
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Cf. A204084.
Sequence in context: A203101 A060691 A075225 * A284494 A091541 A094354
Adjacent sequences: A204075 A204076 A204077 * A204079 A204080 A204081
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin, Jan 10 2012
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STATUS
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approved
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