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A187512
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Number of 7-step S, E, and NW-moving king's tours on an n X n board summed over all starting positions.
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1
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0, 0, 20, 330, 1224, 2726, 4807, 7458, 10679, 14470, 18831, 23762, 29263, 35334, 41975, 49186, 56967, 65318, 74239, 83730, 93791, 104422, 115623, 127394, 139735, 152646, 166127, 180178, 194799, 209990, 225751, 242082, 258983, 276454, 294495
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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) = 285*n^2 - 1624*n + 2210 for n>5.
G.f.: x^3*(1 + x)*(20 + 250*x + 44*x^2 - 20*x^3 - 9*x^4) / (1 - x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>8.
(End)
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EXAMPLE
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Some solutions for 4 X 4:
..0..0..0..0....1..2..0..0....0..5..3..1....0..0..1..2....4..5..6..0
..0..7..0..0....0..3..4..0....0..6..4..2....0..7..5..3....2..3..7..0
..1..5..6..0....0..7..5..0....0..7..0..0....0..0..6..4....0..1..0..0
..2..3..4..0....0..0..6..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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