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A223773
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Number of n X 4 0..1 arrays with rows and columns unimodal and antidiagonals nondecreasing.
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1
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11, 56, 180, 461, 1040, 2164, 4246, 7950, 14308, 24877, 41945, 68796, 110045, 172055, 263449, 395731, 584031, 847990, 1212802, 1710431, 2381022, 3274526, 4452560, 5990524, 7979998, 10531443, 13777231, 17875030, 23011571, 29406825, 37318619
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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) = (1/40320)*n^8 + (1/3360)*n^7 + (19/2880)*n^6 + (7/120)*n^5 + (2447/5760)*n^4 + (259/160)*n^3 + (126691/10080)*n^2 - (12329/840)*n + 13 for n>1.
G.f.: x*(11 - 43*x + 72*x^2 - 67*x^3 + 53*x^4 - 50*x^5 + 34*x^6 - 6*x^7 - 5*x^8 + 2*x^9) / (1 - x)^9.
a(n) = 9*a(n-1) - 36*a(n-2) + 84*a(n-3) - 126*a(n-4) + 126*a(n-5) - 84*a(n-6) + 36*a(n-7) - 9*a(n-8) + a(n-9) for n>10.
(End)
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EXAMPLE
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Some solutions for n=3:
..1..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..1..0..0
..0..0..1..0....0..0..1..1....1..1..0..0....0..1..0..0....1..1..0..0
..0..1..1..1....0..1..1..0....1..1..0..0....1..1..0..0....1..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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