I have investigated Challenge 1 (the Regular numbers) reasonably thoroughly,
building and comparing 4 iterative solutions to generate them.  I also
investigated a Lazy List version, storing the tail of the list as a promise -
a function to call when you wanted the next head item, and the returned tail
is another promise - to generate the next item later when needed.  However,
I couldn't get that to work so abandoned it:-)

Challenge 2 (Pascal's Triangle) by contrast is pretty basic and simple-minded.