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A223944
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Number of n X 3 0..1 arrays with diagonals and antidiagonals unimodal and rows nondecreasing.
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1
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4, 16, 54, 177, 596, 2024, 6869, 23285, 78942, 267681, 907708, 3078001, 10437337, 35392507, 120014445, 406963770, 1379996360, 4679507294, 15868004855, 53807711762, 182459601684, 618712543947, 2098027226581, 7114318736716
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 4*a(n-1) - 2*a(n-2) - a(n-3) + 5*a(n-4) - 8*a(n-5).
Empirical g.f.: x*(4 - 2*x^2 - 3*x^3 - 8*x^4) / (1 - 4*x + 2*x^2 + x^3 - 5*x^4 + 8*x^5). - Colin Barker, Aug 24 2018
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EXAMPLE
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Some solutions for n=3:
..0..1..1....0..0..0....1..1..1....0..0..0....0..1..1....0..0..0....1..1..1
..0..0..1....0..0..1....1..1..1....0..0..1....1..1..1....1..1..1....0..0..0
..0..1..1....1..1..1....0..0..1....0..0..1....1..1..1....0..0..0....0..0..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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