Selecting pairs with composite sums
Source: Kyiv City MO 2022 Round 1, Problem 10.2, 11.2
January 23, 2022
number theory
Problem Statement
You are given distinct integers. What's the largest integer such that you can always form at least pairs from them, so that no integer is in more than one pair, and the sum of integers in each pair is a composite number?(Proposed by Anton Trygub)