Difference between revisions of "1993 IMO Problems/Problem 5"

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==Problem==
 
==Problem==
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Let <math>\mathbb{N} = \{1,2,3, \ldots\}</math>. Determine if there exists a strictly increasing function <math>f: \mathbb{N} \mapsto \mathbb{N}</math> with the following properties:
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(i) <math>f(1) = 2</math>;
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(ii) <math>f(f(n)) = f(n) + n, (n \in \mathbb{N})</math>.
  
 
==Solution==
 
==Solution==

Revision as of 02:10, 5 July 2020

Problem

Let $\mathbb{N} = \{1,2,3, \ldots\}$. Determine if there exists a strictly increasing function $f: \mathbb{N} \mapsto \mathbb{N}$ with the following properties:

(i) $f(1) = 2$;

(ii) $f(f(n)) = f(n) + n, (n \in \mathbb{N})$.

Solution