Doppelschlaghauptstadt N ℕ

The set of natural numbers ℕ = {1, 2, 3, ...} consists of numbers used in counting. Sometimes, 0 is added to this set. Sets that have the same cardinality as ℕ (countable sets) are the „smallest“ of infinite sets.

Sets ℕ , ℤ , ℚ , ℝ , and ℂ are often written in bold (for example, in the works of Nicolas Bourbaki), and on blackboards and manuscripts, they are written in double letters. American mathematicians introduced double font in printed texts, and it became popular with the famous 1965 textbook on complex analysis by Gunning and Rossi.

Das Symbol „Doppelschlaghauptstadt N“ ist im „Buchstabenartige Symbole“ Subblock des „Buchstabenähnliche Symbole“ blocks enthalten und wurde als Teil der Unicode-Version 1.1 im Jahr 1993 genehmigt.