A187194 Number of 7-turn rook's tours on an n X n board summed over all starting positions.

0, 0, 2304, 156672, 2169600, 15220800, 72182880, 264520704, 806827392, 2144534400, 5120913600, 11222069760

Offset

1,3

Links

Table of n, a(n) for n=1..12.

Formula

Empirical G.f.: -96*x^3*(287*x^5+4491*x^4+11886*x^3+8776*x^2+1416*x+24)/(x-1)^9. [Colin Barker, Jul 01 2012]

Example

Some solutions for 3X3
..2..1..0....1..2..0....0..2..1....0..0..4....5..4..0....4..3..5....4..1..5
..3..6..7....6..0..7....5..3..4....1..2..3....6..0..7....7..1..6....0..7..6
..4..5..0....5..3..4....6..0..7....7..6..5....2..3..1....0..2..0....3..2..0

Crossrefs

Row 7 of A187189.

Sequence in context: A235419 A229698 A236280 * A170785 A259321 A223302

Adjacent sequences: A187191 A187192 A187193 * A187195 A187196 A187197

Keyword

nonn,more

Author

R. H. Hardin, Mar 06 2011

Status

approved