

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).


1



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
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OFFSET

1,6


LINKS

Table of n, a(n) for n=1..25.
A. Flammenkamp, Solutions of the nothreeinline problem
A. Flammenkamp, Progress in the nothreeinline problem, J. Combinat. Theory A 60 (1992), 305311.
A. Flammenkamp, Progress in the nothreeinline problem. II, J. Combin. Theory Ser. A 81 (1998), no. 1, 108113.


CROSSREFS

Cf. A000769.
Sequence in context: A211365 A346498 A213135 * A248061 A267500 A300016
Adjacent sequences: A037184 A037185 A037186 * A037188 A037189 A037190


KEYWORD

nonn,more


AUTHOR

N. J. A. Sloane.


EXTENSIONS

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


STATUS

approved



