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A256817
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Number of length n+2 0..1 arrays with at most two downsteps in every n consecutive neighbor pairs.
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1
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8, 16, 32, 64, 124, 229, 402, 673, 1080, 1670, 2500, 3638, 5164, 7171, 9766, 13071, 17224, 22380, 28712, 36412, 45692, 56785, 69946, 85453, 103608, 124738, 149196, 177362, 209644, 246479, 288334, 335707, 389128, 449160, 516400, 591480, 675068
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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) = (1/120)*n^5 + (1/24)*n^4 + (3/8)*n^3 - (1/24)*n^2 + (277/60)*n + 3.
Empirical g.f.: x*(8 - 32*x + 56*x^2 - 48*x^3 + 20*x^4 - 3*x^5) / (1 - x)^6. - Colin Barker, Jan 21 2018
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EXAMPLE
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Some solutions for n=4:
..0....0....1....0....0....0....1....1....0....0....1....0....0....1....0....0
..0....0....1....0....0....1....0....1....1....0....0....1....1....1....0....1
..0....1....1....1....1....0....0....1....0....0....0....0....1....0....0....0
..0....0....1....0....0....0....1....0....1....1....0....1....0....0....0....0
..0....1....0....0....0....1....1....0....1....0....1....0....1....0....0....1
..1....1....0....1....0....1....1....0....0....1....1....1....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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