Almost right-angled triangles I
Problem 223Published on Friday, 26th December 2008, 05:00 pm; Solved by 972; Difficulty rating: 70%
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?