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Mathematics-Online lexicon:

Countable Sets

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z overview

A set $ A$ is countable if $ A$ is finite or if there exists a bijective map

$\displaystyle f: \mathbb{N} \longmapsto A $

that is

$\displaystyle A = \{a_1,a_2,\ldots\} $

with $ a_i=f(i)$.
(Authors: Kimmerle/Abele)
[Examples] [Links]
  automatically generated 6/11/2007