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A188778
Number of 3-turn bishop's tours on an n X n board summed over all starting positions
1
0, 0, 28, 152, 488, 1192, 2468, 4560, 7760, 12400, 18860, 27560, 38968, 53592, 71988, 94752, 122528, 156000, 195900, 243000, 298120, 362120, 435908, 520432, 616688, 725712, 848588, 986440, 1140440, 1311800, 1501780, 1711680, 1942848, 2196672
OFFSET
1,3
COMMENTS
Row 3 of A188777
LINKS
FORMULA
Empirical: a(n) = 4*a(n-1) -5*a(n-2) +5*a(n-4) -4*a(n-5) +a(n-6)
Contribution from Vaclav Kotesovec, Sep 01 2012: (Start)
Empirical: G.f.: 4*x^3*(7 + 10*x + 5*x^2)/((1-x)^5*(1+x))
Empirical: a(n) = 1/4 - 10*n/3 + 23*n^2/3 - 20*n^3/3 + 11*n^4/6 - (-1)^n/4
(End)
EXAMPLE
Some solutions for 4X4
..0..0..0..0....0..0..0..1....1..0..0..0....0..0..0..0....0..0..2..0
..1..0..0..0....0..0..0..0....0..3..0..0....3..0..0..0....0..0..0..3
..0..3..0..0....0..2..0..0....0..0..0..0....0..1..0..0....1..0..0..0
..0..0..2..0....0..0..3..0....0..0..0..2....0..0..2..0....0..0..0..0
CROSSREFS
Sequence in context: A028380 A219887 A271636 * A002593 A015881 A026910
KEYWORD
nonn
AUTHOR
R. H. Hardin Apr 10 2011
STATUS
approved