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 A328818 #12 May 09 2020 02:32:20 %S A328818 0,2,1,-1,-2,-1,1,3,4,3,2,0,-2,-3,-4,-3,-2,0,2,4,5,6,5,4,3,1,-1,-3,-4, %T A328818 -5,-6,-5,-4,-3,-1,1,3,5,6,7,8,7,6,5,4,2,0,-2,-4,-5,-6,-7,-8,-7,-6,-5, %U A328818 -4,-2,0,2,4,6,7,8,9,10,9,8,7,6,5,3,1,-1,-3,-5,-6,-7,-8,-9,-10,-9,-8,-7,-6,-5,-3,-1 %N A328818 2 * x-coordinate of the points of a counterclockwise spiral on an hexagonal grid. %C A328818 The Cartesian coordinates of the points of a counterclockwise spiral on an hexagonal grid are given by x(n) = a(n)/2 and by y(n)= A307012(n) * sqrt(3)/2. %H A328818 Hugo Pfoertner, <a href="/A328818/b328818.txt">Table of n, a(n) for n = 0..10000</a> %H A328818 Hugo Pfoertner, <a href="/A328818/a328818.pdf">Illustration of spiral</a>. %H A328818 <a href="/index/Con#coordinates_2D_curves">Index entries for sequences related to coordinates of 2D curves</a> %F A328818 a(n) = A307011(n) + A307013(n). %Y A328818 Cf. A307011, A307012, A307013. %K A328818 sign %O A328818 0,2 %A A328818 _Hugo Pfoertner_, Oct 28 2019