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A256819
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Number of length n+4 0..1 arrays with at most two downsteps in every n consecutive neighbor pairs.
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1
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32, 64, 128, 256, 484, 856, 1424, 2249, 3402, 4965, 7032, 9710, 13120, 17398, 22696, 29183, 37046, 46491, 57744, 71052, 86684, 104932, 126112, 150565, 178658, 210785, 247368, 288858, 335736, 388514, 447736, 513979, 587854, 670007, 761120, 861912
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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 + (1/8)*n^4 + (27/8)*n^3 - (65/8)*n^2 + (1897/60)*n + 3 for n>2.
Empirical g.f.: x*(32 - 128*x + 224*x^2 - 192*x^3 + 68*x^4 - 4*x^6 + x^7) / (1 - x)^6. - Colin Barker, Jan 21 2018
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EXAMPLE
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Some solutions for n=4:
..1....1....1....0....0....1....0....1....1....0....0....1....0....0....0....0
..0....0....0....1....0....0....1....1....1....0....0....0....1....0....1....1
..0....1....0....1....0....0....0....0....0....0....1....1....1....0....1....1
..1....1....0....1....1....0....0....0....0....0....0....1....0....0....1....0
..1....0....0....1....1....0....0....1....0....0....0....0....1....1....1....1
..0....0....0....0....1....0....0....0....0....0....0....1....1....1....0....0
..0....0....0....1....0....1....1....0....1....0....0....1....1....0....1....1
..1....1....1....0....1....1....0....1....1....1....1....0....1....0....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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