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A256820
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Number of length n+5 0..1 arrays with at most two downsteps in every n consecutive neighbor pairs.
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1
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64, 128, 256, 512, 956, 1656, 2693, 4158, 6153, 8792, 12202, 16524, 21914, 28544, 36603, 46298, 57855, 71520, 87560, 106264, 127944, 152936, 181601, 214326, 251525, 293640, 341142, 394532, 454342, 521136, 595511, 678098, 769563, 870608, 981972
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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 + (1/6)*n^4 + (175/24)*n^3 - (103/6)*n^2 + (747/10)*n - 30 for n>3.
Empirical g.f.: x*(64 - 256*x + 448*x^2 - 384*x^3 + 124*x^4 + 16*x^5 - 7*x^6 - 8*x^7 + 4*x^8) / (1 - x)^6. - Colin Barker, Jan 21 2018
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EXAMPLE
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Some solutions for n=4:
..0....1....0....0....0....1....0....1....0....1....1....0....1....1....0....1
..0....0....0....1....0....0....0....1....1....0....1....0....0....0....0....0
..0....0....0....0....1....1....0....0....1....1....1....0....1....0....1....1
..1....0....0....0....0....1....1....0....0....1....0....0....1....1....1....0
..1....0....1....1....0....1....1....1....0....0....1....1....1....1....1....1
..0....1....0....0....0....1....1....1....0....1....0....1....0....1....0....1
..1....1....1....1....0....1....0....0....0....0....1....1....1....0....1....0
..1....0....0....1....0....0....0....1....0....0....0....1....0....1....0....1
..1....1....0....0....0....0....1....0....0....1....1....1....1....1....1....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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