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Number of nonequivalent ways to place n points on an n X n square grid so that no more than 2 points are on a vertical or horizontal straight line.
7

%I #7 Dec 23 2016 18:55:28

%S 1,2,14,202,4361,126396,4444935,182567862,8560638040,451107721000

%N Number of nonequivalent ways to place n points on an n X n square grid so that no more than 2 points are on a vertical or horizontal straight line.

%C Rotations and reflections of placements are not counted. If they are to be counted, see A279444.

%e There are a(3) = 14 nonequivalent ways to place 3 points on a 3 X 3 square grid under the condition mentioned above:

%e XX XX. XX. XX. XX. XX. X.X X.X X X X.. X.. X.. .X. .X.

%e ..X ... X.. .X. ... ... .X. ... ... .XX .X. ..X XX. X.X

%e ... ..X ... ... X.. .X. ... X.. .X. ... ..X .X. ... ...

%Y Cf. A279444, A279453.

%K nonn,more

%O 1,2

%A _Heinrich Ludwig_, Dec 23 2016