Question: Maple getting stuck when changing limits of sum

When I type the command

sum(2^n, n=0..N)

Maple calculates it correctly. However, if I then go back to that expression and click on it to change the value of N, Maple tries to execute something before I hit enter. It won't stop unless I press the Interrupt button, and after that I have to insert some other calculation, e.g. 1+1, for it to work once again.

This happens even on completely new files and for any explicit values of N.

Why is this happening?

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