1/A = 1/B + 1/C.
Let B=A+X. Then 1/A = 1/(A+X) + 1/C. C = 1/(1/A - 1/(A+X)) = A(A+X)/(A+X-A) = A^2/X + A. C is an integer when X is a factor of A^2.
So all {A,B,C} can be expressed as {A,A+X,A^2/X + A} with A^2 mod X = 0.
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flooble's webmaster puzzle