We show that triangle-free penny graphs have degeneracy at most two, list
coloring number (choosability) at most three, diameter D=Ω(n), and
at most min(2n−Ω(n),2n−D−2) edges.Comment: 10 pages, 2 figures. To appear at the 25th International Symposium on
Graph Drawing and Network Visualization (GD 2017