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A218587
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Hilltop maps: number of n X 3 binary arrays indicating the locations of corresponding elements not exceeded by any horizontal or antidiagonal neighbor in a random 0..2 n X 3 array.
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1
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7, 57, 449, 3567, 28305, 224643, 1782855, 14149449, 112295673, 891223263, 7073103393, 56134970523, 445509522567, 3535741318617, 28061053779825, 222703718478543, 1767465563243697, 14027311885918707, 111326343684867783
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OFFSET
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1,1
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COMMENTS
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Column 3 of A218592.
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LINKS
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R. H. Hardin, Table of n, a(n) for n = 1..210
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FORMULA
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Empirical: a(n) = 7*a(n-1) + 7*a(n-2) + 3*a(n-3) + 3*a(n-4) + 3*a(n-5).
Empirical g.f.: x*(7 + 8*x + x^2 + 4*x^3 + x^4) / (1 - 7*x - 7*x^2 - 3*x^3 - 3*x^4 - 3*x^5). - Colin Barker, Jul 24 2018
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EXAMPLE
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Some solutions for n=3:
..1..0..0....0..1..1....1..0..1....0..1..0....1..1..1....1..1..1....1..1..1
..0..1..0....0..1..1....0..0..1....1..1..1....0..1..0....0..1..1....0..0..1
..1..1..1....0..1..0....1..0..1....0..0..0....0..1..1....0..0..0....1..0..1
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CROSSREFS
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Cf. A218592.
Sequence in context: A202510 A042187 A201872 * A218838 A082310 A014990
Adjacent sequences: A218584 A218585 A218586 * A218588 A218589 A218590
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin, Nov 03 2012
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STATUS
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approved
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