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Z is infinite but it is countable because we can define

f: N ->bijective Z
f(x) := if x is even then -x/2 else (x+1)/2
f = [0, 1, -1, 2, -2, 3, -3, ...].

While Z is infinite, we can enumerate all its elements.

Author: Wolfgang Schreiner
Last Modification: December 7, 1999

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