Difference between Two Squares equal to Repunit/Mistake

Source Work

 * The Dictionary
 * $111$
 * $111$

Mistake

 * $111 = 20^2 - 17^2$, the third difference of $2$ squares equal to a repunit. The sequence of such squares starts $1, 0$; $6, 5$; $20, 17$; $56, 45$; $156, 115$; $344, 85$; $356, 125 \ldots$

The instance $56^2 - 55^2 = 111$ has been omitted.

This omission does not originate from -- for some reason it does not appear in the list generated by  and.