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A297219
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Number of n X 3 0..1 arrays with every 1 horizontally or antidiagonally adjacent to 1 neighboring 1s.
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1
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3, 8, 24, 68, 196, 564, 1620, 4660, 13396, 38516, 110740, 318388, 915412, 2631924, 7567124, 21756468, 62552660, 179847028, 517083540, 1486682292, 4274404564, 12289467892, 35333815316, 101589305140, 292082437972, 839774919796
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OFFSET
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1,1
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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) = a(n-1) + 4*a(n-2) + 4*a(n-3).
Empirical g.f.: x*(3 + 5*x + 4*x^2) / (1 - x - 4*x^2 - 4*x^3). - Colin Barker, Feb 26 2019
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EXAMPLE
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Some solutions for n=7:
..0..0..0. .0..1..1. .1..1..0. .0..0..0. .0..1..0. .1..1..0. .1..1..0
..1..1..0. .0..0..1. .0..0..0. .0..1..1. .1..0..1. .0..0..0. .0..0..0
..0..0..0. .0..1..0. .0..1..0. .0..0..0. .0..1..0. .0..1..1. .1..1..0
..0..1..0. .0..1..1. .1..0..0. .1..1..0. .0..0..0. .0..0..0. .0..0..0
..1..0..0. .0..0..0. .1..1..0. .0..1..1. .0..1..1. .0..1..0. .0..1..1
..0..1..0. .0..0..0. .0..0..0. .0..0..0. .0..0..0. .1..0..0. .0..0..1
..1..0..0. .0..0..0. .0..0..0. .0..1..1. .1..1..0. .0..1..1. .0..1..0
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CROSSREFS
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Column 3 of A297224.
Sequence in context: A176904 A056332 A091588 * A018046 A095125 A078055
Adjacent sequences: A297216 A297217 A297218 * A297220 A297221 A297222
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin, Dec 27 2017
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STATUS
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approved
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