A187302 Number of 7-step one space leftwards or up, two space rightwards or down asymmetric rook's tours on an n X n board summed over all starting positions.

0, 0, 108, 1368, 6264, 15596, 31172, 52256, 79634, 112568, 151266, 195512, 245332, 300704, 361628, 428104, 500132, 577712, 660844, 749528, 843764, 943552, 1048892, 1159784, 1276228, 1398224, 1525772, 1658872, 1797524, 1941728, 2091484, 2246792

Offset: 1

Author

R. H. Hardin, Mar 08 2011

Keywords

• nonn

Comments

Row 7 of A187296.

Examples

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

Links

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

Crossrefs

Cf. A187296.

Formula

Empirical: a(n) = 2776*n^2 - 19580*n + 30728 for n>11.

Conjectures from Colin Barker, Apr 23 2018: (Start)

G.f.: 2*x^3*(54 + 522*x + 1242*x^2 + 400*x^3 + 904*x^4 - 368*x^5 + 393*x^6 - 369*x^7 + 104*x^8 - 108*x^9 + 13*x^10 - 11*x^11) / (1 - x)^3.

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>14.

(End)