The Bell numbers, also known as the exponential numbers, were studied extensively by mathematician Eric Temple Bell.
The Bell numbers are obtained by extracting the factors and altering the denominators of the power series for exp(exp(x)).
Bell numbers have various applications, including determining the number of ways to partition a set of labeled items and representing moments of a Poisson random variable.
Bell's triangle, similar to Pascal's triangle, can also be created to generate the Bell numbers.