Vertical axis: number of protons (atomic number); horizontal axis: number of neutrons. Colored non-gray nuclei indicate experimentally identified nuclides (3150); the region of the slanted rectangle corresponds to the main part of the chart. The gray region indicates nuclides whose existence has been theoretically predicted through calculation with the Koura－Tachibana－Uno－Yamada (KTUY) mass model, which was developed at the Advanced Science Research Center (ASRC) with collaborators.