what is this madness

Ok, I see, easy fix and I passed. Thanks.

i'm sorry, this is my fault; the assertion message was incorrect when n > 254, and the memory was not reset at every test, which caused confusing assertions

I fixed that and republished. Your code is still wrong though, for the reason I said.

That doesn't seem to be the issue, as the error appears for n = 254: for n = 254, at index 232, expected: "#e9e9e9" but got: ""
the index where it doesn't find any entry seems to change everytime I run it, attempting again, I get for n = 254, at index 193, expected: "#c2c2c2" but got: "".

you have to generate shades even when n is larger than 254, it's just that you stop at 254

Thanks for this, the comments are nice xxx

If you program recursively, the intermediate fractions need to be stored in memory. But this probably only takes up a little more space on the stack until the function finally returns, so even with millions of calls it doesn't really matter.

Nice demonstration of xlat!