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PROJECT EULER · #0397

Triangle on Parabola

Statement only · UnsolvedOriginal problem ↗

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 1kK and Xa<b<cX.

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

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