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A187156
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Number of 3-step one space at a time bishop's tours on an n X n board summed over all starting positions.
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2
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0, 0, 20, 64, 132, 224, 340, 480, 644, 832, 1044, 1280, 1540, 1824, 2132, 2464, 2820, 3200, 3604, 4032, 4484, 4960, 5460, 5984, 6532, 7104, 7700, 8320, 8964, 9632, 10324, 11040, 11780, 12544, 13332, 14144, 14980, 15840, 16724, 17632, 18564, 19520, 20500
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OFFSET
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1,3
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 12*n^2 - 40*n + 32 for n>1.
G.f.: 4*x^3*(5 + x) / (1 - x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>4.
(End)
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EXAMPLE
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Some solutions for 4 X 4:
..0..0..0..3....0..0..3..0....1..0..0..0....0..1..0..3....0..1..0..0
..0..0..2..0....0..2..0..0....0..2..0..0....0..0..2..0....0..0..2..0
..0..1..0..0....0..0..1..0....3..0..0..0....0..0..0..0....0..3..0..0
..0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..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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