@Glorfindel This edit seemed a bit unusual to me: mathoverflow.net/posts/43754/revisions Specifically, replacing the Wikipedia link by Wayback Machine link.

Of course, I can understand that it might be useful to have the version at the time when the question was posted. But if I was considering adding such link, I would probably opted for the specific revision on Wikipedia rather than for Wayback Machine.

But I'm not sure that this was the intention here.

Interestingly, the old link doesn't work for me:

@MartinSleziak that one does, thanks for spotting that.

@Glorfindel Yes, you're right. When I go to revision 1, I get the same error (Bad Title).

Before I posted here, I looked only at the current revision - I clicked on your Wayback Machine link and then tried to remove the "Wayback" part from the URL.

My bad for assuming that the original link and the last part of the Wayback Machine link were the same.

Probably some sanitation on Wayback Machine's part ...

specific-question What are your favorite puzzles/toys for introducing new mathematical concepts to students? This question was bumped today. Would recreational-mathematics be suitable there?