I am sorry, it's like 5 years back when I did it, and I don't remember (nor I am inclined in pursuing it further). (I didn't gave up because it became impossible, I just became less interested.)

But lot of those harder ones - as far as I can tell - required pretty deep knowledge of number theory, which even though I studied math (10 years ago), didn't have. I think it would be nice if there was sometimes a hint about what the people should study to be able to solve it.

I became obsessed with this problem recently:

http://projecteuler.net/problem=436

and couldn't solve it. I found an article on mathworld that says the number of expected rolls is e so that the sum is over 1. I don't know how to figure out what the value of the roll that gets you over 1 is, it's something like 0.64 from simulation but what does that number mean and why?

I have the same problem, this one for instance http://projecteuler.net/problem=267 I have absolutely no clue how to approach.