also: ししょくもんだい
noun
four-color problem; four-color map problem
A famous problem in mathematics (graph theory) asking whether four colors suffice to color any planar map so that no two adjacent regions share the same color. Proved in 1976.
四色問題は、1976年にコンピュータを使って証明された。
The four-color problem was proved in 1976 using a computer.
四色問題はグラフ理論の有名な未解決問題だった。
The four-color problem was a famous unsolved problem in graph theory.