Sea Wasp wrote:

I don't recall Star Trek having anything involving Fermat's Last
Theorem.

As they say, Google is your friend:

The Royale

In this episode, Picard is studying Fermat's Great Theorem, and says it
has remained unsolved for 800 years. Five years after the episode was
made the theorem was actually solved, by Andrew Wiles and Richard
Taylor from Princeton University. In the Star Trek universe, this was
referred to in an episode of Deep Space Nine, and is considered as a
subtle correction for Picard's statements.

When I saw this episode, I yelled at the screen that everyone knows
that Fermat had been proven in the 21st century. So, I was wrong also.
My reasoning was that Ribet had very recently proven that
Taniyama-Shimura implies Fermat, and I thought sometime in the 21st
century Taniyama-Shimura was likely to be proven. It didn't seem like
1987 was a very good year to commit to the proposition that Fermat was
still going to be open by Picard's day, though I doubt very much anyone
connected with the show knew of Ribet's work, which was not yet
published.