A037186 Number of ways of placing 2n points on n X n grid so no 3 are in a line (solutions with symmetry about one main diagonal).

0, 0, 0, 0, 2, 0, 1, 5, 3, 3, 6, 3, 9, 5, 13, 14, 12, 14, 16, 17, 13, 18, 34, 43, 55, 42, 44, 59, 53, 88, 65

Offset

1,5

Links

Table of n, a(n) for n=1..31.

A. Flammenkamp, Solutions of the no-three-in-line problem

A. Flammenkamp, Number of Solutions of the No-Three-in-Line-Problem on Small Grids

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.

Sequence in context: A163940 A112340 A356264 * A343239 A004483 A197808

Adjacent sequences: A037183 A037184 A037185 * A037187 A037188 A037189

Keyword

nonn,more,changed

Author

N. J. A. Sloane

Extensions

a(26)-a(31) from Flammenkamp's website, added by David Radcliffe, Jun 19 2026

Status

approved