%I
%S 1,2,4,6,8,10,12,14,16,18
%N Size of the largest subset S of the points of an n X n square grid such that no three of the points of S form an isosceles triangle.
%C S must not contain 3 points A,B,C such that AB = BC.
%C For example, this configuration is forbidden:
%C O O O B
%C O O O O
%C A O O O
%C O C O O
%C It appears that this is simply a(n) = 2n2 for n>1, and if so this entry may be replaced by a comment in A271914 and A271906, and this Anumber recycled.
%e Illustration for a(3) = 4:
%e O X X
%e X O O
%e X O O
%e Illustration for a(8) = 14:
%e O X X X X X O X
%e X O O O O O O X
%e X O O O O O O O
%e X O O O O O O O
%e X O O O O O O O
%e X O O O O O O O
%e O O O O O O O O
%e X X O O O O O O
%Y Cf. A271906, A227133.
%Y Main diagonal of A271914.
%K nonn,more
%O 1,2
%A _Giovanni Resta_ and _N. J. A. Sloane_, Apr 22 2016
