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A271907 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. 3

%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) = 2n-2 for n>1, and if so this entry may be replaced by a comment in A271914 and A271906, and this A-number 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

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Last modified September 17 16:45 EDT 2021. Contains 347487 sequences. (Running on oeis4.)