# Squares

You have a $$10 \times 10$$ grid containing the numbers 1 - 100 as shown below, all in order, except that 13 is switched with 40, (in red).

Now for the question...

How many ways can you pick two different $$3 \times 3$$ groups of 9 numbers (like the one in green above) such that the sum of the 9 numbers inside is the same for both of them?

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