How good are you in Ellipse

From a point on the axis of x common tangent are drawn to the parabola $y^{2} = 4x$ and the ellipse $\frac{x^{2}}{a^{2}} + \frac{y^{2}}{b^{2}} = 1$ $(a>b>0)$ . If tangent form an equilateral triangle with their chord of contact with respect to parabola, then set of exhaustive values of a is: $( \frac{p}{q}, r)$ Find $( p + q + r)$

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