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 A018810 #18 Nov 29 2017 09:22:21 %S A018810 0,0,0,8,4,16,36,64,100,204,252,396,572,780,1020,1484,1756,2260,2828, %T A018810 3540,4332,5556,6372,7716,9188,10684,12292,14684,16588,19324,22268, %U A018810 25420,28780,33164,36452,41036,45892,51324,57060,64540,70500,77724,85300,93228 %N A018810 Number of lines through exactly 3 points of an n X n grid of points. %D A018810 Lucien Pianaro, Jouer Jeux Mathematiques, 9(juillet 1993). [From _Philippe Deléham_, Apr 10 2009] %H A018810 Seiichi Manyama, <a href="/A018810/b018810.txt">Table of n, a(n) for n = 0..1000</a> %H A018810 S. Mustonen, <a href="http://www.survo.fi/papers/PointsInGrid.pdf">On lines and their intersection points in a rectangular grid of points</a> [From _Seppo Mustonen_, Apr 18 2009] %F A018810 a(n) = 1/2 (f(n, 4) - 2 f(n, 3) + f(n, 2)) where f(n, k) = Sum ((n - |kx|)(n - |ky|)); -n<kx<n, -n<ky<n, (x, y)=1. [From _Seppo Mustonen_, Apr 18 2009] %Y A018810 Cf. A119437. %K A018810 nonn %O A018810 0,4 %A A018810 _David W. Wilson_