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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 4 of A187189

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..28

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

Sequence in context: A060355 A060859 A187289 * A054607 A254408 A132592

Adjacent sequences:  A187188 A187189 A187190 * A187192 A187193 A187194

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 06 2011

STATUS

approved

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Last modified February 24 04:18 EST 2020. Contains 332195 sequences. (Running on oeis4.)