Vol XXX 2020 – 2021

Geombinatorics

A quarterly journal on open problems of combinatorial and discrete geometry and related areas.

July 2020 – April 2021

Issue 1   Issue 2   Issue 3    Issue 4 


Issue 1 (July 2020)


CONTENTS XXIX (1)

Editor’s Page………………….………………………………..….4

New Essays

A small 6-chromatic unit-distance graph in R3……………………………..5

by Aubrey de Grey

Polyiamonds Attaining Extremal Topological
Properties, Part I…………………………………………………………….……….…14

by Greg Malen and Érika Roldán

What percent of the plane can be properly 5- and
6-colored?……….…………………………………………………………………………25

by Jaan Parts

Moral Principles for My Young Colleagues, or
A Tale of Big Man and Little Bird………………………………….……….……40

by Alexander Soifer   

New Subscription Form…………….……….………………………47


Issue 2  (October 2020)


Editor’s Page………………….…………………………………49

New Essays

Remembering John Horton Conway……………………………………………..53
by Alexander Soifer

Remembering Ronald Lewis Graham………………………………………….56
by Alexander Soifer

Polyiamonds Attaining Extremal Topological Properties,
Part II……………………………………………………………………………………………..63
by Greg Malen and Érika Roldán

The chromatic number of the plane is at least 5
a human-verifiable proof………………………………………………………………77
by Jaan Parts

New Subscription Form…………………………………………………………………103


Issue 3 (January 2021)


Editor’s Page………………….…………………………………

New Essays

       Recent Books…………………………………………….…

Subscription Form…………….……….………………………


Issue 4 (April 2021)

CONTENTS XXIX (4)

Editor’s Page………………….………………………………..….

New Essays

       Recent Books…………………………………………….…

Subscription Form…………….……….………………………