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A203184
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Number of nX1 0..4 arrays with every nonzero element less than or equal to some horizontal or vertical neighbor
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1
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1, 5, 25, 95, 325, 1121, 3985, 14288, 50995, 181336, 644721, 2294193, 8166441, 29066618, 103444256, 368138471, 1310164527, 4662787112, 16594519920, 59058487061, 210183969235, 748026706926, 2662163892493, 9474416502527
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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) = 5*a(n-1) -10*a(n-2) +20*a(n-3) -15*a(n-4) +21*a(n-5) -7*a(n-6) +8*a(n-7) -a(n-8) +a(n-9).
Empirical g.f.: -x*(1+x^2)*(x^6+6*x^4+9*x^2+1) / ( -1+5*x-10*x^2+20*x^3-15*x^4+21*x^5-7*x^6+8*x^7-x^8+x^9 ). - R. J. Mathar, Jul 02 2013
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EXAMPLE
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Some solutions for n=4
..2....0....4....0....4....0....2....4....0....0....2....1....0....1....3....2
..2....1....4....4....4....1....2....4....3....4....4....3....1....2....3....2
..1....2....1....4....4....4....1....1....4....4....4....4....4....2....2....3
..0....2....1....4....4....4....0....0....4....4....4....4....4....0....0....3
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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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