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A187378
Number of 4-step S, NW and NE-moving king's tours on an n X n board summed over all starting positions
1
0, 4, 40, 132, 278, 478, 732, 1040, 1402, 1818, 2288, 2812, 3390, 4022, 4708, 5448, 6242, 7090, 7992, 8948, 9958, 11022, 12140, 13312, 14538, 15818, 17152, 18540, 19982, 21478, 23028, 24632, 26290, 28002, 29768, 31588, 33462, 35390, 37372, 39408
OFFSET
1,2
COMMENTS
Row 4 of A187377
LINKS
FORMULA
Empirical: a(n) = 27*n^2 - 97*n + 88 for n>2.
Empirical G.f.: 2*x^2*(2+14*x+12*x^2-x^3)/(1-x)^3. [Colin Barker, Jan 22 2012]
EXAMPLE
Some solutions for 4X4
..0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..2....4..0..0..0
..3..0..0..0....0..0..2..0....0..0..0..0....0..0..1..3....0..3..0..0
..4..2..0..0....0..0..3..1....3..1..0..0....0..0..0..4....0..0..2..0
..0..0..1..0....0..0..4..0....4..2..0..0....0..0..0..0....0..0..0..1
CROSSREFS
Sequence in context: A069539 A063997 A355841 * A199833 A248964 A224086
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 09 2011
STATUS
approved