A187190 Number of 3-turn rook's tours on an n X n board summed over all starting positions.

0, 8, 108, 480, 1400, 3240, 6468, 11648, 19440, 30600, 45980, 66528, 93288, 127400, 170100, 222720, 286688, 363528, 454860, 562400, 687960, 833448, 1000868, 1192320, 1410000, 1656200, 1933308, 2243808, 2590280, 2975400

Offset: 1

Author

R. H. Hardin, Mar 06 2011

Keywords

• nonn

Examples

			Some solutions for 3X3
..0..0..3....0..2..3....1..0..2....0..0..3....0..3..0....0..0..0....3..2..0
..0..1..2....0..1..0....0..0..0....0..0..2....0..2..1....0..2..3....0..0..0
..0..0..0....0..0..0....0..0..3....0..0..1....0..0..0....0..1..0....0..1..0
		

Crossrefs

Row 3 of A187189.

Formula

Empirical: a(n) = 4*n^4 - 10*n^3 + 6*n^2.

Empirical G.f.: 4*x^2*(2+17*x+5*x^2)/(1-x)^5. - Colin Barker, Jan 22 2012