Exactly how bad is the 13 times table?

Let’s recite the $13$ times table. Pay attention to the first digit of each number: \begin{array}{l} \color{blue}13, \\ \color{blue}26, \\ \color{blue}39, \\ \color{blue}52 \end{array} What happened to $\color{blue}4$‽ A while ago I was working through the $13$ times table for some boring reason, and I was in the kind of mood to find it really quite vexing... Read more »