This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A235457 #10 Nov 16 2016 15:51:45 %S A235457 1,142,4699,77970,672506,4338248,21167201,85351595,294664274, %T A235457 911848844,2528561187,6501165477 %N A235457 Number of non-equivalent (mod D_4) ways to arrange 6 points on an n X n square grid so that no three points are collinear. %C A235457 Column 6 of A235453. %C A235457 Without the restriction "non-equivalent (mod D_4)" the numbers are given by A194191, n >= 3. %e A235457 There is a(3) = 1 way to place 6 points (X) on a 3 X 3 grid (without rotations and reflections): %e A235457 . X X %e A235457 X . X %e A235457 X X . %Y A235457 Cf. A235453, A194191, A235454 (3 points), A235455 (4 points), A235456 (5 points), A235458 (7 points). %K A235457 nonn,more %O A235457 3,2 %A A235457 _Heinrich Ludwig_, Jan 12 2014 %E A235457 a(13), a(14) from _Heinrich Ludwig_, Nov 16 2016