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A266357
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Number of n X 3 binary arrays with rows and columns lexicographically nondecreasing and row and column sums nondecreasing.
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1
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4, 13, 35, 82, 173, 337, 614, 1060, 1749, 2777, 4266, 6369, 9273, 13206, 18441, 25302, 34170, 45490, 59776, 77620, 99698, 126778, 159728, 199525, 247262, 304159, 371571, 450998, 544095, 652683, 778758, 924504, 1092303, 1284747, 1504650, 1755061
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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) = 5*a(n-1) -9*a(n-2) +6*a(n-3) -6*a(n-7) +9*a(n-8) -5*a(n-9) +a(n-10).
Empirical g.f.: x*(4 - 7*x + 6*x^2 - 6*x^6 + 9*x^7 - 5*x^8 + x^9) / ((1 - x)^7*(1 + x)*(1 + x + x^2)). - Colin Barker, Jan 09 2019
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EXAMPLE
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Some solutions for n=4:
..0..0..1....0..0..0....0..0..1....0..0..1....0..0..1....0..0..0....0..0..0
..0..0..1....0..0..1....0..1..1....0..1..0....0..1..1....0..0..1....0..0..0
..0..1..0....0..1..1....1..1..1....0..1..0....1..0..1....0..0..1....0..1..1
..1..0..1....1..1..0....1..1..1....1..0..1....1..1..1....0..1..1....1..1..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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