A037187 Number of ways of placing 2n points on n X n grid so no 3 are in a line (solutions with 180 deg rotational symmetry).

0, 0, 0, 1, 0, 2, 10, 7, 7, 13, 30, 33, 82, 61, 283, 189, 282, 328, 594, 675, 2413, 1248, 3968, 2852, 8983

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• more

Links

• A. Flammenkamp, Solutions of the no-three-in-line problem
• A. Flammenkamp, Progress in the no-three-in-line problem, J. Combinat. Theory A 60 (1992), 305-311.
• A. Flammenkamp, Progress in the no-three-in-line problem. II, J. Combin. Theory Ser. A 81 (1998), no. 1, 108-113.

Crossrefs

Cf. A000769.

Extensions

There are published versions of this sequence which incorrectly give 693 instead of 675.