![combinatorics - A formula for the number of possible combinations of a $i\times j$ rectangle in a $m\times n$ grid such that they don't overlap? - Mathematics Stack Exchange combinatorics - A formula for the number of possible combinations of a $i\times j$ rectangle in a $m\times n$ grid such that they don't overlap? - Mathematics Stack Exchange](https://i.stack.imgur.com/cVmHk.png)
combinatorics - A formula for the number of possible combinations of a $i\times j$ rectangle in a $m\times n$ grid such that they don't overlap? - Mathematics Stack Exchange
How many combinations are there if you have 10 numbers (you must use all ten at the same time)? - Quora
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