Because Google+ has been scheduled for shutdown (see item below), I’ve started cross-posting links to my Mastodon account @11011110@mathstodon.xyz in the hope that this gives me a smooth transition plan when the shutdown occurs. It also lets me put math formulas into my posts! Those new cross-posts are where the little $\mathbb{M}$ links on some of the entries below go. So if you want to see these postings when I make them, rather than these later roundups, follow me there.

• Crooked Timber on algorithms (G+). This piece on algorithmic decision-making makes the point that the kind of “algorithm” used for these tasks is very different from the historical meaning of the word, and that these methods are likely to fall into the same errors that have painstakingly been weeded out from more principled statistical methods in social science and economics.

• More than 9 million broken links on Wikipedia are now rescued (G+, via). The internet archive continues to be extremely useful, in this case for rescuing broken links from Wikipedia articles. (I’m also a big fan of its collection of out-of-copyright books.)

• Twenty geometry puzzles by Catriona Shearer on Math with Bad Drawings (G+, via). I like the ones from this set where you can get the answer with a quick flash of insight and very little calculation. The one below is one of those. Or maybe they all are, and I just haven’t found the insights for all of them?