What is your favorite Project Euler question?
- by A. Rex
I was searching around for questions related to Project Euler on Stack Overflow, and it seems that there were plenty of people asking about it, and even more people recommending it, whether for fun, to learn a new language, or to practice for interview questions. All this seems to imply to me that there are lots of people on SO that solve Project Euler problems now and then. I just started, so I was wondering:
What was your favorite Project Euler question? Why? Did you think of a clever trick, or did you learn some new math, or did you discover a feature of a new programming language?
(If possible, please include the actual question in your answer.)