Problem 4
Find all positive integers such that can be partitioned into two disjoint sets whose products are equal.
Step 2 of 4: Find the forced odd term
In plain words
The three odd positions must distribute the only possible odd prime factors, leaving one factor-free odd number.
Detailed analysis
There are three odd numbers. At most one is divisible by , and at most one by . Therefore one odd number has neither factor nor factor ; it also has no factor . With the restriction above, that number must be .