13. Let point $A_{0}$ be at the origin of the Cartesian coordinate system, and $A_{1}, A_{2}, \cdots$, $A_{n}, \cdots$ be sequentially on the positive half of the $x$-axis, with $\left|A_{n-1} A_{n}\right|=2 n-1$, $n=1,2, \cdots$. Construct equilateral triangles $A_{n-1} A_{n} B_{n}$ above the $x$-axis with $A_{n-1} A_{n}$ as the base. Then the equation of the parabola passing through all points $B_{1}, B_{2}, \cdots, B_{n}, \cdots$ is $\qquad$.
13. $y^{2}=3\left(x-\frac{1}{4}\right)$