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