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 A292276 #10 Sep 21 2017 15:30:43 %S A292276 1,4,4,8,12,12,12,12,20,12,20,20,20,20,20,20,20,24,28,20,20,20,36,36, %T A292276 28,20,36,36,36,36,28,36,36,36,44,36,36,36,36,52,44,36,36,36,52,44,52, %U A292276 52,44,52,44,60,52,44,52,44,52,52,52,52,60,52,52,52,68,44 %N A292276 a(n) = number of vertices of the convex hull of the set of points of norm <= n^2 in square lattice. %C A292276 The convex hull of a finite point set in dimension 2, say S, forms a convex polygon whose vertices are in S. %C A292276 For any n >= 0, A000328(n) gives the number of elements of the set of points of norm <= n^2 in square lattice. %C A292276 For symmetry reasons, a(n) is a multiple of 4 for any n > 0. %H A292276 Rémy Sigrist, <a href="/A292276/a292276.txt">C++ program for A292276</a> %H A292276 Rémy Sigrist, <a href="/A292276/a292276.png">Illustration of the convex hulls for n=0..10</a> %H A292276 Wikipedia, <a href="https://en.wikipedia.org/wiki/Convex_hull#Convex_hull_of_a_finite_point_set">Convex hull of a finite point set</a> %e A292276 See Links section. %o A292276 (C++) See Links section. %Y A292276 Cf. A000328, A046109. %K A292276 nonn %O A292276 0,2 %A A292276 _Rémy Sigrist_, Sep 13 2017