Natural number
From specialfunctionswiki
The natural numbers $\mathbb{N}$ is the set $$\mathbb{N}=\{0,1,2,\ldots\}.$$ Note: many references do not include $0$ in the set of natural numbers. We use the term "positive integers" for the set $\mathbb{Z}^+=\{1,2,3,\ldots\}$.
