Unformatted text preview: terms: A = { a 1 , a 2 , a 3 , . . . } . E XAMPLE 4.28 The integers Z are countable, since they can be listed as: , 1 ,1 , 2 ,2 , 3 ,3 , . . . This ‘counting’ function can be deFned formally by the bijection g : Z → N deFned by g ( x ) = 2 x, x ≥ =12 x, x < E XAMPLE 4.29 The set of integers Z is like two copies of the natural numbers N . We can even count N 2 , which is like N copies of N , as illustrated by the following diagram: 1 2 3 4 1 2 3 4 41...
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 Spring '09
 Koskesh
 Math, Natural Numbers, Sets, Natural number, Countable set, infinite sets

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