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Triangle on parabola

Problem 397

Published on 07 October 2012 at 05:00 am [Server Time]

On the parabola y = x2/k, three points A(a, a2/k), B(b, b2/k) and C(c, c2/k) are chosen.

Let F(K, X) be the number of the integer quadruplets (k, a, b, c) such that at least one angle of the triangle ABC is 45-degree, with 1 ≤ k ≤ K and -X ≤ a < b < c ≤ X.

For example, F(1, 10) = 41 and F(10, 100) = 12492.
Find F(106, 109).


Answer:
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