For a general $2$ by $2$ square, the column headings could be $x$
and $(x + 1)$, and the row headings could be $y$ and $(y +
1)$.
For a general $3$ by $3$ square, the column headings could be $x$,
$(x + 1)$ and $(x + 2)$, and the row headings could be $y$, $(y +
1)$ and $(y + 2)$.