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URL: https://oeis.org/A187191

⇱ A187191 - OEIS

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A187191
Number of 4-turn rook's tours on an n X n board summed over all starting positions.
1
0, 8, 288, 2208, 9200, 27720, 68208, 146048, 282528, 505800, 851840, 1365408, 2101008, 3123848, 4510800, 6351360, 8748608, 11820168, 15699168, 20535200, 26495280, 33764808, 42548528, 53071488, 65580000, 80342600, 97651008
OFFSET
1,2
LINKS
FORMULA
Empirical: a(n) = 8*n^5 - 34*n^4 + 48*n^3 - 22*n^2.
Empirical g.f.: 8*x^2*(1+30*x+75*x^2+14*x^3)/(1-x)^6. - Colin Barker, Jan 22 2012
EXAMPLE
Some solutions for 3X3
..0..4..0....2..1..0....0..1..2....1..0..0....0..0..4....4..2..3....3..2..0
..2..3..1....3..0..0....4..0..3....2..3..4....0..1..2....0..0..0....0..0..0
..0..0..0....4..0..0....0..0..0....0..0..0....0..0..3....0..1..0....4..1..0
CROSSREFS
Row 4 of A187189.
Sequence in context: A060355 A060859 A187289 * A054607 A254408 A132592
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 06 2011
STATUS
approved