Reading the comments as a mathematician... yup they're tough and require enough knowledge that I know they'll be challenging the next time around.

Reading this as a computer scientist: Knuth is where the education is at. And like project Euler, don't feel bad if you miss a few of the hard ones.

I was trained in computational number theory, and when I used them to teach myself ruby, and I stopped when I got comfortable enough with the language to find the problems tiring