Abstract
Erdős number, which is defined as the distance between one scientist and Paul Erdős, is one of the most famous scientific jokes. The collaboration graph to define Erdős number consists of researchers as vertices, and the edge is drawn between two vertices if the two researchers jointly authored one or more papers. Erdős number is frequently mentioned as the typical example of small world phenomenon, and is the good educational tool to learn about relationship among various academic disciplines. In this study, to clarify the position of informational chemistry in science, Erdős numbers of Japanese informational chemists were discussed. Hosoya number was introduced and the Erdős number can be approximately obtained by using Hosoya number.
