I'd say 100 solved problems is pretty impressive. I have about 75-ish done with no math background (other than a few classes for my CS degree).

The first 50 should be doable for most people in my opinion. After that you need to start being really clever or actually going and researching the problem at hand.

For which people?

There are certain "developers" who can't even fizz buzz their way out of a paper bag.

Let's say for someone you think is competent.

Not scores so much as specific problems.

If I work on it for a week, get frustrated, google for solutions, and can't find any, and you solved it, you're a beast.

Also if you solve 328 tell me how. And no, dynamic programming is not efficient enough.

It's easier than you might think. Only read this comment as far as you need to make a little more progress. These hints only apply if you're starting with a dynamic programming approach. Also, they're only helpful if you do the work, so I don't think they violate the spirit of Project Euler.

Is your dynamic programming table 2D? Maybe it should be.

Stop reading if that's progress.

Have you looked closely at the table content?

Stop reading.

Have you noticed how similar many parts are, under perhaps simple transforms?

Stop reading.

Try adding or subtracting your coordinates, to see more of the pattern.

Stop reading.

There's not just a within-row pattern.

Stop reading.

In the end, dynamic programming might not be the main trick. But you can make your own way from here.

Maybe there is a closed-form solution?

I did the first 50 problems, and then cherry picked another 15 or so.

At some point the math was beyond my knowledge, and I didn't find much fun in researching it.

I'm a fairly normal web developer, in my own estimation.

It's really tough to say. Some people have awesome math degrees, some people only do it casually, some don't do it at all.

Keep doing the problems until you get stuck. Then learn, then solve a few more. Repeat as long as you're happy with your progress. I wouldn't put a number on it.

In fact, do some easy ones in a completely new language!