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A218190
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Hilltop maps: number of nX2 binary arrays indicating the locations of corresponding elements not exceeded by any horizontal or vertical neighbor in a random 0..3 nX2 array
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2
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3, 15, 63, 251, 1001, 4001, 16001, 63985, 255867, 1023171, 4091495, 16361227, 65425905, 261627633, 1046206665, 4183611549, 16729587163, 66898918163, 267517973263, 1069761185739, 4277802274577, 17106240667845, 68405094720089
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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) = 3*a(n-1) +3*a(n-2) +3*a(n-3) +3*a(n-4) +3*a(n-5) +2*a(n-6) +2*a(n-7) -a(n-8) -a(n-9) -a(n-10) -a(n-11) -a(n-12) -a(n-13)
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EXAMPLE
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Some solutions for n=3
..0..1....1..1....0..0....0..1....0..0....1..0....0..0....1..0....0..1....1..0
..0..1....0..0....1..0....0..1....0..1....0..0....1..1....0..1....1..1....1..0
..1..0....0..1....0..0....1..1....1..1....1..0....0..0....1..0....0..1....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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