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A265988
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Number of n X 4 integer arrays with each element equal to the number of horizontal and antidiagonal neighbors not equal to itself.
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1
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1, 2, 2, 2, 7, 7, 21, 35, 78, 158, 323, 682, 1395, 2920, 6035, 12551, 26048, 54067, 112291, 233073, 483986, 1004757, 2086142, 4331198, 8992360, 18669984, 38762260, 80478161, 167087798, 346906568, 720244459, 1495365541, 3104666070, 6445881590
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OFFSET
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1,2
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LINKS
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FORMULA
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Empirical: a(n) = a(n-1) + 2*a(n-2) + a(n-3) - a(n-5) - 3*a(n-6) + a(n-7).
Empirical g.f.: x*(1 + x - 2*x^2 - 5*x^3 - x^4 - 5*x^5 + 3*x^6) / ((1 - x)*(1 - 2*x^2 - 3*x^3 - 3*x^4 - 2*x^5 + x^6)). - Colin Barker, Jan 09 2019
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EXAMPLE
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Some solutions for n=7:
..1..3..1..1....1..3..1..1....1..3..1..1....1..2..2..1....1..3..1..1
..1..1..3..1....1..1..3..1....1..1..4..2....1..1..1..1....1..1..3..1
..1..3..1..1....1..3..1..1....1..3..3..1....1..3..3..1....1..3..1..1
..1..1..4..2....1..1..3..2....1..1..1..1....1..1..1..1....1..1..4..2
..1..3..3..1....1..3..4..1....1..3..3..1....1..3..3..1....1..3..3..1
..1..1..1..1....1..1..1..1....1..1..1..1....1..1..1..1....2..4..1..1
..1..2..2..1....1..2..2..1....1..2..2..1....1..2..2..1....1..1..3..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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