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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).
1

%I #9 Dec 02 2018 04:09:04

%S 0,0,0,1,0,2,10,7,7,13,30,33,82,61,283,189,282,328,594,675,2413,1248,

%T 3968,2852,8983

%N 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).

%H A. Flammenkamp, <a href="http://wwwhomes.uni-bielefeld.de/achim/no3in/table.txt">Solutions of the no-three-in-line problem</a>

%H A. Flammenkamp, <a href="https://doi.org/10.1016/0097-3165(92)90012-J">Progress in the no-three-in-line problem</a>, J. Combinat. Theory A 60 (1992), 305-311.

%H A. Flammenkamp, <a href="https://doi.org/10.1006/jcta.1997.2829">Progress in the no-three-in-line problem. II</a>, J. Combin. Theory Ser. A 81 (1998), no. 1, 108-113.

%Y Cf. A000769.

%K nonn,more

%O 1,6

%A _N. J. A. Sloane_.

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