Volume XXVIII

VOL XXVIII

Geombinatorics Quarterly

Issue 1 (July 2018)

Progress in My Favorite Open Problem of Mathematics, Chromatic
Number of the Plane: An Étude in Five Movements 		 By Alexander Soifer  5
The Chromatic Number of the Plane Is at least 5 By Aubrey D.N.J. de Grey 18
Computing Small Unit-Distance Graphs with Chromatic
Number 5		 By Marijn J.H. Heule 32
The Hadwiger-Nelson problem with two
forbidden distances		 By Geoffrey Exoo and Dan Ismailescu 51

Issue 2 (October 2018)

The Chromatic Number of  The Taxicab Plane By John Donnelly 77
A note on the clique chromatic number of geometric graphs  By Jacob Fox, János Pach, and Andrew Suk 83
Two Consequences of the Recent Discovery that x(r2,1)>4 By Peter Johnson 87
Extensions of Möbius-Kantor Configurations By J. Lanyon and R. Padmanabhan 93
Why Asset-Based Approach to Teaching Is More Effective
than the Usual Deficit-Based Approach, and Why the New
Approach Is Not Easy to Implement: A Simple Geometric
Explanation 		By Olga Kosheleval and Vladik Kreinovich 99
Truth, Like Water, Finds Its Way Out By Alexander Soifer 106
Revisiting Bodies having Constant HA-Measurements By Joseph Zaks 112

Issue 3 (January 2019)

[4,3]-Configurations with Many Symmetries By Branko Grünbaum  
Branko Grünbaum, a Fantastic Father as well as Renowned Mathematician By Rami Grunbaum with Daniel Grünbaum 121
Inseparability By Sarah Zaks 124
Branko By Moshe Rosenfeld 127
Branko Grünbaum in Many Dimensions By Matthew Kahle 132
Branko, My Teacher, Collaborator, and Friend By Alexander Soifer 139
Numbers of Crossings for Cycle Graphs By Alewyn P. Burger, Elie Feder, and Heiko Harborth 150

Issue 4 (April 2019)

Avoiding monochromatic configurations in the multi-colored plane By Seung Hwan An, Dan Ismailescu, and Kwon Il Ko   177
On the Independence Numbers of the Van der Waerden and cyclic Van der Waerden Hypergraphs W(k; t) and Wc(k; t) when t and k Are Powers of the Same Prime By Peter Johnson and Zechun Yang  191
Tiling the plane with equilateral triangles By János Pach and Gábor Tardo 201
Chromatic Problems and Prizes By Alexander Soifer 210
Revisiting the 2d Neighborly d-simplices in Ed By Joseph Zaks 215