Difference between revisions of "2005 Canadian MO Problems/Problem 5"

 
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Revision as of 19:33, 28 July 2006

Problem

Let's say that an ordered triple of positive integers $(a,b,c)$ is $n$-\emph{powerful} if $a \le b \le c$, $\gcd(a,b,c) = 1$, and $a^n + b^n + c^n$ is divisible by $a+b+c$. For example, $(1,2,2)$ is 5-powerful.

  • Determine all ordered triples (if any) which are $n$-powerful for all $n \ge 1$.
  • Determine all ordered triples (if any) which are 2004-powerful and 2005-powerful, but not 2007-powerful.

Solution

See also