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 A385160 #10 Jul 24 2025 09:31:52 %S A385160 4,68,4244,38100,222300,695544,2252764 %N A385160 Place a point on the integer coordinates, up to |n|, along all four axial directions on a Cartesian plane, and then join a circle through every unordered triple of non-collinear points: a(n) is the number of distinct points where circles intersect. %H A385160 Scott R. Shannon, <a href="/A385160/a385160.jpg">Image for n = 2</a>. The 4 x 2 = 8 starting points are shown as white dots. %H A385160 Scott R. Shannon, <a href="/A385160/a385160_1.jpg">Image for n = 3</a>. The 4 x 3 = 12 starting points are shown as white dots. %F A385160 a(n) = A385162(n) - A385161(n) + 1 by Euler's formula. %Y A385160 Cf. A385159 (total circles), A385161 (regions), A385162 (edges), A384703, A383461, A374825, A359569. %K A385160 nonn,more %O A385160 1,1 %A A385160 _Scott R. Shannon_, Jul 10 2025