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A284076
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Number of 2Xn 0..1 arrays with no 1 equal to more than three of its horizontal, diagonal and antidiagonal neighbors, with the exception of exactly two elements.
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1
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0, 0, 1, 6, 33, 176, 858, 4000, 18298, 82176, 363027, 1584090, 6844659, 29327056, 124752876, 527398452, 2217568396, 9279837664, 38668567653, 160517532910, 664042452165, 2738524464624, 11261702650622, 46191451640392
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OFFSET
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1,4
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 9*a(n-1) -24*a(n-2) +30*a(n-3) -84*a(n-4) +48*a(n-5) +106*a(n-6) +318*a(n-7) +813*a(n-8) +919*a(n-9) +990*a(n-10) +756*a(n-11) +216*a(n-12).
Empirical g.f.: x^2*(-1 +3*x -3*x^2 +7*x^3 +30*x^4 +32*x^5 +12*x^6)/ (6*x^4+7*x^3+x^2+3*x-1)^3 . - R. J. Mathar, Mar 21 2017
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EXAMPLE
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Some solutions for n=4
..1..1..1..1. .0..1..1..1. .1..1..1..0. .1..1..1..1. .1..1..1..0
..0..1..1..1. .1..1..1..1. .1..1..1..1. .1..1..1..0. .1..1..1..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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