A279452 Number of nonequivalent ways to place n points on an n X n square grid so that no more than 2 points are on a vertical or horizontal straight line.

1, 2, 14, 202, 4361, 126396, 4444935, 182567862, 8560638040, 451107721000

Offset: 1

Author

Heinrich Ludwig, Dec 23 2016

Keywords

• nonn
• more

Comments

Rotations and reflections of placements are not counted. If they are to be counted, see A279444.

Examples

			There are a(3) = 14 nonequivalent ways to place 3 points on a 3 X 3 square grid under the condition mentioned above:
XX   XX.  XX.  XX.  XX.  XX.  X.X  X.X  X X  X..  X..  X..  .X.  .X.
..X  ...  X..  .X.  ...  ...  .X.  ...  ...  .XX  .X.  ..X  XX.  X.X
...  ..X  ...  ...  X..  .X.  ...  X..  .X.  ...  ..X  .X.  ...  ...
		

Crossrefs

Cf. A279444, A279453.