In the following equation $x$, $y$, and $n$ are positive integers.

$${\displaystyle \frac{1}{x}}+{\displaystyle \frac{1}{y}}={\displaystyle \frac{1}{n}}$$

For a limit $L$ we define $F(L)$ as the number of solutions which satisfy $x<y\le L$.

We can verify that $F(15)=4$ and $F(1000)=1069$.
Find $F({10}^{12})$.