Category Archives: chatter

Superpermutations: lower bound

Posted on 2018-10-20 by

I wrote about superpermutations here: a superpermutation is a string that has as substrings all the permutations of some set of symbols. For example, there are six permutations of the symbols 1, 2, 3. They are: 123, 132, 213, 231, … Continue reading →

Posted in chatter | 4 Comments

Squares of squares, and the group of rational points on the circle

Posted on 2016-08-02 by

The purpose of this post is to describe a slightly different way of thinking about the existence – or otherwise – of a 3×3 magic square of squares. Of course it may not lead to any real progress, but it … Continue reading →

Posted in chatter, Mathematics | 1 Comment

Almost-magic squares of squares

Posted on 2016-07-18 by

In the last post we saw that every 3×3 almost-magic square is a rearrangement of three three-term arithmetic progressions that have the same common difference. In other words, if we pick any three numbers x, y and z, and any … Continue reading →

Posted in chatter, Mathematics | 2 Comments

Magic squares of squares: Part I

Posted on 2016-07-13 by

A recent Numberphile video discussed an intriguing unsolved problem in number theory: is there a 3×3 magic square whose entries are all square numbers? (Matt Parker proposed a solution which doesn’t quite work: see the video for more. The “Parker … Continue reading →

Posted in chatter, Mathematics | 2 Comments

The Government Statistical Service’s terrible spreadsheet advice

Posted on 2014-12-05 by

The UK Government Statistical Service recently released its good practice guidance for releasing statistics in spreadsheets. While this advice is clearly well-intentioned*, and parts of it are good, the overall effect is to encourage the release of data in formats … Continue reading →

Posted in chatter, Kiln | 6 Comments

Tackling the Minimal Superpermutation Problem

Posted on 2014-08-22 by

What’s the shortest string that contains every possible permutation of ABCD somewhere inside it? As it happens, it’s 33 letters long: ABCDABCADBCABDCABACDBACBDACBADCBA. A string like this is called a minimal superpermutation. So what’s the shortest string that contains every possible … Continue reading →

Posted in chatter, Mathematics, news | 6 Comments

I hate the Pumping Lemma

Posted on 2013-08-18 by

I hate the Pumping Lemma for regular languages. It’s a complicated way to express an idea that is fundamentally very simple, and it isn’t even a very good way to prove that a language is not regular. Here it is, … Continue reading →

Posted in chatter | 45 Comments