A212807 Number of ways to place 2n points on a 2n X 2n square array of points such that no three points are collinear and the configuration has 90-degree rotational symmetry.

1, 1, 3, 4, 7, 4, 13, 13, 7, 16, 8, 23, 36, 58, 92, 101, 172, 281, 337, 541, 746

Offset: 1

Author

N. J. A. Sloane, May 29 2012

Keywords

• nonn
• more
• fini

Comments

No such arrangement is possible on a 2n+1 X 2n+1 grid.

Links

• D. B. Anderson, Sample solutions for n = 18, 20, 22, 24, 26
• David Brent Anderson Update on the no-three-in-line problem, J. Combin. Theory Ser. A 27 (1979), no. 3, 365--366. MR0555806(81g:05055).
• A. Flammenkamp, Solutions of the no-three-in-line problem

Crossrefs

Cf. A000769.

Extensions

a(11)-a(21) from Giovanni Resta, Mar 22 2013 (data from A. Flammenkamp's website)