The non-TRVG conjecture for $D^a_n$ in the remaining range

Let $D^a_n$ denote the graph used in the paper, with parameters $a$ and $n$. A non-TRVG is a graph that is not a transparent rectangle visibility graph. The conjecture concerns integers satisfying

$$2a+5\le n\le 2a+7\quad\text{and}\quad a\ge 3.$$

The $D^a_n$ non-TRVG conjecture. $D^a_n$ is a non-TRVG when $2a+5\le n\le 2a+7$ and $a\ge 3$.

The paper proves that $D^a_n$ is a non-TRVG for $n\ge 2a+8$ and a TRVG for $n\le 2a+4$, leaving this intermediate range as the stated conjecture.