Geombinatorics Quarterly

Issue 1 (July 2019)

Polyominoes with maximally many holes By Matthew Kahle and Érika Roldán     5
Generalizations of the No-Three-in-a-Line Problem By Dustin LaFollette and Anant Godbole 21
The Smallest Art Gallery Not Guarded by Every Third
Vertex		 By Ralph Morrison      24
The International Mathematics Union Abacus Medal By Alexander Soifer    33
On a Geometric Proof of Sums of Powers By Joseph Zaks 37

Issue 2 (October 2019)

Coloring Distance Graphs on the Integers By Matthew Ellison, Joseph Johnson 49
Fission of Halving Edges Graphs By Tanya Khovanova and Dai Yang 56
4-Regular Planar Unit Triangle Graphs without Additional Triangles

By Mike Winkler, Peter Dinkelacker, and Stefan Vogel

 72
Dynamic Triggering of Earthquakes: Symmetry-Based Geometric Analysis

By Laxman Bokati, Richard Alfaro, Aaron Velasco, and Vladik Kreinovich

 78

Issue 3 (January 2020)

A 6-chromatic two-distance graph in the plane By Geoffrey Exoo and Dan Ismailescu 97
Nonlinear Mechanical Properties of Road Pavements: Geometric Symmetries Explain the Empirical Difference Between Roads Built on Clay vs. Granular Soils By  Afshin Gholamy and Vladik Kreinovich 104
A Small 6-Chromatic Two-Distance Graph in the Plane By Jaan Parts 111
A 3-Regular Matchstick Graph of Girth 5 Consisting of 54 Vertices By Mike Winkler, Peter Dinkelacker, and Stefan Vogel 116
On the Cyclic Van der Waerden NumberWc(4; 2) By Carson Wood 122

Issue 4 (April  2020)

Graph minimization, focusing on the example of 5-chromaticunit-distance graphs in the plane By by Jaan Parts 137
A Square-Grid Coloring Problem
Properties, Part I		 By Matthew Kahle, Francisco Martinez-Figueroa, and Alexander Soifer 167