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A195233
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Number of lower triangles of a 3 X 3 0..n array with each element differing from all of its diagonal, vertical, antidiagonal and horizontal neighbors by one or less.
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1
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64, 155, 246, 337, 428, 519, 610, 701, 792, 883, 974, 1065, 1156, 1247, 1338, 1429, 1520, 1611, 1702, 1793, 1884, 1975, 2066, 2157, 2248, 2339, 2430, 2521, 2612, 2703, 2794, 2885, 2976, 3067, 3158, 3249, 3340, 3431, 3522, 3613, 3704, 3795, 3886, 3977
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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) = 91*n - 27.
G.f.: x*(64 + 27*x) / (1 - x)^2.
a(n) = 2*a(n-1) - a(n-2) for n>2.
(End)
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EXAMPLE
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Some solutions for n=4:
..2......1......0......2......1......3......2......0......4......3......0
..2.3....2.1....0.1....1.1....0.0....2.2....2.1....0.1....3.3....4.3....0.0
..2.3.3..1.1.2..0.1.1..2.2.1..0.0.0..2.2.1..2.1.1..1.0.0..3.4.4..3.3.4..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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