A187287 Number of 2-step one or two space at a time rook's tours on an n X n board summed over all starting positions.

0, 8, 36, 80, 140, 216, 308, 416, 540, 680, 836, 1008, 1196, 1400, 1620, 1856, 2108, 2376, 2660, 2960, 3276, 3608, 3956, 4320, 4700, 5096, 5508, 5936, 6380, 6840, 7316, 7808, 8316, 8840, 9380, 9936, 10508, 11096, 11700, 12320, 12956, 13608, 14276, 14960, 15660

Offset: 1

Author

R. H. Hardin, Mar 08 2011

Keywords

• nonn

Examples

			Some solutions for 4 X 4:
..0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..2..0..1
..1..0..0..0....0..1..0..0....0..1..2..0....2..0..0..0....0..0..0..0
..0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0
..2..0..0..0....0..2..0..0....0..0..0..0....1..0..0..0....0..0..0..0
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..50

Crossrefs

Row 2 of A187286.

Cf. A014107.

Programs

Maple

A187287:=n->`if`(n=1, 0, 8*n^2 - 12*n); seq(A187287(n), n=1..50); # Wesley Ivan Hurt, Feb 28 2014

Formula

Empirical: a(n) = 8*n^2 - 12*n for n>1.

Empirical g.f.: 4*x^2*(2+3*x-x^2)/(1-x)^3. - Colin Barker, Jan 22 2012