What is the probability that in a group of 200 people, at least 2 of them have the same initials?
I'm finding the probability to be about .679. Is this correct?
Just a caveat about real-world probabilities. (It's not clear whether this is a textbook exercise or a real-world problem.)
In the "real world", initials are anything but uniformly distributed; there are far more S's then Z's, for example. If you want a real-world answer, you will need to find some data on the distribution of initials and take that into account.