A328818 - OEIS

%I #12 May 09 2020 02:32:20

%S 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 -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 -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 2 * x-coordinate of the points of a counterclockwise spiral on an hexagonal grid.

%C 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 Hugo Pfoertner, <a href="/A328818/b328818.txt">Table of n, a(n) for n = 0..10000</a>

%H Hugo Pfoertner, <a href="/A328818/a328818.pdf">Illustration of spiral</a>.

%H <a href="/index/Con#coordinates_2D_curves">Index entries for sequences related to coordinates of 2D curves</a>

%F a(n) = A307011(n) + A307013(n).

%Y Cf. A307011, A307012, A307013.

%K sign

%O 0,2

%A _Hugo Pfoertner_, Oct 28 2019