Problem 223
Almost right-angled triangles I

Let us call an integer sided triangle with sides a ≤b ≤c barely acute if the sides satisfy
a2 + b2 = c2 + 1.

How many barely acute triangles are there with perimeter ≤ 25,000,000?

These problems are part of Project Euler and are licensed under CC BY-NC-SA 2.0 UK