Pythagorean triples

1. wiki:

• https://en.wikipedia.org/wiki/Pythagorean_triple
• https://en.wikipedia.org/wiki/Tree_of_primitive_Pythagorean_triples

2. Euclid's formula is a fundamental formula for generating Pythagorean triples given an arbitrary pair of positive integers m and n with m > n.

• a = m^2 - n^2
• b = 2mn
• c = m^2 + n^2

where m and n is coprime and odd parity.

How to iterate all coprime pairs:

• Farey sequence
• wiki: https://en.wikipedia.org/wiki/Farey_sequence
• Counting
• https://primes.utm.edu/notes/relprime.html
• 6 / pi^2

3. Counting:

• https://projecteuler.net/problem=540