MathDB
Fatal Numbers

Source: Indonesian National Mathematical Olympiad 2024, Problem 2

August 28, 2024
number theoryInamoprimesfactorizationsIndonesiaNT constructionIndonesia MO

Problem Statement

The triplet of positive integers (a,b,c)(a,b,c) with a<b<ca<b<c is called a fatal triplet if there exist three nonzero integers p,q,rp,q,r which satisfy the equation apbqcr=1a^p b^q c^r = 1. As an example, (2,3,12)(2,3,12) is a fatal triplet since 2231(12)1=12^2 \cdot 3^1 \cdot (12)^{-1} = 1. The positive integer NN is called fatal if there exists a fatal triplet (a,b,c)(a,b,c) satisfying N=a+b+cN=a+b+c. (a) Prove that 16 is not fatal. (b) Prove that all integers bigger than 16 which are not an integer multiple of 6 are fatal.