Bell numbers

Bell numbers are a sequence of numbers that represent the number of ways to partition a set into non-empty subsets. In simpler terms, they count how many different ways you can group a set of items without caring about the order of the groups. For example, for a set of three items, there are five ways to divide them into groups. Bell numbers grow rapidly, and they have applications in various fields such as combinatorics, computer science, and probability, helping to understand complex structures and problems related to grouping and organizing data.