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A218228
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Hilltop maps: number of nX3 binary arrays indicating the locations of corresponding elements not exceeded by any horizontal, vertical or antidiagonal neighbor in a random 0..2 nX3 array
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1
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7, 61, 497, 3969, 31739, 253825, 2029849, 16232833, 129815047, 1038139593, 8302071585, 66392220265, 530943014251, 4245986702321, 33955438893389, 271543909879097, 2171554761048415, 17366068280933465, 138877606472351657
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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) = 7*a(n-1) +7*a(n-2) +7*a(n-3) +5*a(n-4) +9*a(n-5) +9*a(n-6) +9*a(n-7) +8*a(n-8) +4*a(n-9) +a(n-10) +a(n-11) +a(n-12) +a(n-13) -a(n-14) -a(n-15) -a(n-16) -a(n-17)
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EXAMPLE
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Some solutions for n=3
..1..1..1....1..1..0....1..1..1....0..1..1....1..1..0....0..0..1....1..1..0
..1..1..0....0..1..1....0..0..0....0..1..0....0..0..0....1..1..0....1..1..1
..0..1..1....0..1..0....0..1..0....0..1..1....0..0..1....1..0..1....0..1..1
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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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