Jaan Parts’ Current World Record

In April 2020 issue of Geombinatorics, Dr. Jaan Parts, a microchip designer-engineer from Kazan, the capital of Tatarstan, Russia, presented an overview and classification of the state of hunting for 5-chromatic unit-distance graphs. I refer you to his 30-page Geombinatorics article [Par2] for important details. Parts’ record holder (in terms of the smallest number of vertices) is a graph on 509 vertices with 2442 edges (visualized in Fig. 56.1), created using a large subgraph on 374 vertices with 1860 edges (visualized in Fig. 56.2), and a small subgraph on 136 vertices with 564 edges (visualized in Fig. 56.3).