What are Pleasant Classes of Mathematics?

Abstract

In this note, we analyze factors in pleasant classes of mathematics. In sections 1 and 2, we sort the factors into two groups. One of them consists of elements in classes, and the other consists of those in pleasant. In each group, we pick up main elements in classes and pleasant, respectively. In section 3, we introduce several examples of methods of classes enhanced by those elements, where we indicate which elements please those classes.