Integer partition

Definition

Let $n$ be a natural number. A partition of $n$ is a finite multiset of positive integers whose sum is $n$. Its elements are the parts of the partition.

Equivalently, a partition of $n$ is a finite sequence $\lambda_1 \ge \lambda_2 \ge \dots \ge \lambda_k$ of positive integers with $\lambda_1 + \dots + \lambda_k = n$.