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A196537
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Number of nX1 0..4 arrays with each element equal to the number its horizontal and vertical neighbors less than or equal to itself
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3
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1, 3, 2, 7, 19, 35, 77, 176, 377, 819, 1801, 3927, 8562, 18711, 40855, 89179, 194729, 425184, 928305, 2026855, 4425441, 9662395, 21096706, 46062279, 100571611, 219586403, 479441557, 1046805072, 2285577449, 4990293595, 10895727817
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = a(n-1) +a(n-2) +3*a(n-3) +a(n-4).
Empirical: G.f. x*(x-1)*(x^2+3*x+1) / ( -1+x+x^2+3*x^3+x^4 ). - R. J. Mathar, Jul 25 2012
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EXAMPLE
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All solutions for n=4
..0....0....1....0....0....1....0
..2....1....0....2....2....1....2
..2....2....2....1....1....2....0
..0....0....0....1....0....0....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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