The 15th pythagorean triple on the Plimpton tablet is not pr

The 15th pythagorean triple on the Plimpton tablet is not primitive. What is the smallest number in the primitive triple it arises from?

Note: 1 is not the answer!

Solution

The relevant Pythagorean triple (28,45, 53) arises from (2pq,p² -q² ,p² +q² ) with p =7 , q=2