Dirichlet Function

math

Definition

Definition

The Dirichlet function, named after Peter Gustav Lejeune Dirichlet, is the indicator function $1_{\mathbb{Q}}$ of the set of rational numbers $\mathbb{Q}$.

$$1_{\mathbb{Q}}(x)=\{\begin{array}{ll}1& x\in \mathbb{Q}\\ 0& x\notin \mathbb{Q}\end{array}$$

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Footnotes

1. Dirichlet function - Wikipedia ↩