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A230930
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Number of black-square subarrays of (n+2) X (3+2) 0..3 arrays x(i,j) with each element diagonally or antidiagonally next to at least one element with value (x(i,j)+1) mod 4, no adjacent elements equal, and upper left element zero.
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1
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8, 16, 102, 232, 1682, 3768, 27106, 60824, 437930, 982552, 7073698, 15870936, 114260634, 256361112, 1845635570, 4140964568, 29812290666, 66888415128, 481553712898, 1080439106264, 7778468998714, 17452180031640, 125644509294994
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = 16*a(n-2) + 3*a(n-4) - 10*a(n-6) + 24*a(n-8) - 16*a(n-10).
Empirical g.f.: 2*x*(4 + 8*x - 13*x^2 - 12*x^3 + 13*x^4 + 4*x^5 - 16*x^6 + 8*x^8) / (1 - 16*x^2 - 3*x^4 + 10*x^6 - 24*x^8 + 16*x^10). - Colin Barker, Sep 23 2018
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EXAMPLE
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Some solutions for n=4:
..x..0..x..0..x....x..0..x..0..x....x..0..x..0..x....x..0..x..0..x
..1..x..1..x..3....3..x..1..x..3....1..x..3..x..1....1..x..1..x..3
..x..2..x..0..x....x..0..x..2..x....x..2..x..2..x....x..2..x..0..x
..3..x..1..x..3....3..x..1..x..3....0..x..0..x..1....1..x..3..x..1
..x..0..x..2..x....x..2..x..0..x....x..1..x..3..x....x..0..x..2..x
..3..x..3..x..1....1..x..1..x..3....0..x..2..x..2....3..x..1..x..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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