Let us suppose that we have an $m\times n$ grid such that every element is a digit in base $10$. Then we can read the numbers from a grid such that we fix a starting element and go to one of the eight nearest grid and maintain that direction. Or, to be precisely, you don't have to go to that direction any steps so you can also read the numbers $1, 4,9$. How small value $mn$ can be such that one can read the numbers $1^2,2^2,3^2,\ldots,100^2$ from the grid?
For example if the grid is
then one can read the squares $1^2,\ldots,10^2$ from it but for example $11^2=121$ is missing. In this rectange $mn=2\cdot 5=10$.