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 A235458 #11 Nov 16 2016 15:51:28 %S A235458 28,3385,134353,1958674,19929645,138586349,753795278,3356614240, %T A235458 13108210508,44374441652,137349454120 %N A235458 Number of non-equivalent (mod D_4) ways to arrange 7 points on an n X n square grid so that no three points are collinear. %C A235458 Column 7 of A235453. %C A235458 Without the restriction "non-equivalent (mod D_4)" the numbers are given by A194192, n >= 4. %e A235458 There are a(4) = 28 non-equivalent ways to place 7 points (X) on a 4 X 4 grid. Example: %e A235458 . X X . %e A235458 . . . X %e A235458 X . . X %e A235458 X X . . %Y A235458 Cf. A235453, A194192, A235454 (3 points), A235455 (4 points), A235456 (5 points), A235457 (6 points). %K A235458 nonn,more %O A235458 4,1 %A A235458 _Heinrich Ludwig_, Jan 12 2014 %E A235458 a(13), a(14) from _Heinrich Ludwig_, Nov 16 2016