That's pythonic beauty in its purest form - well done!!

Thanks for the note. I assume I did not think it all the way through.

Have you already tried your proposal? Because I just did, and I could not get it to work with sqrt(n).

Thanks for explaining!

I'm just wondering as I am scrolling trough one of my python books (which focus on best practice), but isn't this solution breaking the Python principal of "Sparse is better than dense?", because there are more then one Statement on each of those lines? And there are multiple exit points where my source tells me it's more Pythonic to keep the exit points to a minimal.

There is no reason to reinvent the wheel. Thats one of the main aspects why python is such a strong programming language.