Difference between revisions of "2022 SSMO Speed Round Problems/Problem 6"
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Revision as of 13:59, 3 July 2023
Problem
Find the smallest odd prime that does not divide .
Solution
Let this odd prime be .
Note that is divisible by if or .
As such, is the smallest prime of the form where is also prime.
This is called a \textit{safe} prime in literature and checking that is the first such .