▾ Set of symbols
▾ Alphabet
▾ Deduction system
▾ Theory
▾ Zermelo-Fraenkel set theory
▾ Set
▾ Collection of sets
▾ Set union
▾ Successor set
▾ Inductive set
▾ Set of inductive sets
▾ Set of natural numbers
▾ Natural number
Fermat number
Formulation 0
A D996: Natural number $n \in \mathbb{N}$ is a Fermat number if and only if \begin{equation} \exists \, m \in \mathbb{N} : 2^{(2^m)} + 1 = n \end{equation}