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PROJECT EULER · #0410

Circle and Tangent Line

Statement only · UnsolvedOriginal problem ↗

Let C be the circle with radius r, x2+y2=r2. We choose two points P(a,b) and Q(a,c) so that the line passing through P and Q is tangent to C.

For example, the quadruplet (r,a,b,c)=(2,6,2,7) satisfies this property.

Let F(R,X) be the number of the integer quadruplets (r,a,b,c) with this property, and with 0<rR and 0<aX.

We can verify that F(1,5)=10, F(2,10)=52 and F(10,100)=3384.
Find F(108,109)+F(109,108).

Write-up coming later

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