I have just spent five days in Columbus, Ohio, at a conference celebrating the sixtieth birthday of Laszlo Babai.

Avid readers of this blog (are there any?) will have come across Laci’s name here before. He is (so far) the only guest contributor; he wrote a reply to my rant about open-access publishing. Also, he comes into my story about Paul Erdős; Laci and I were workig together in an office in Montréal when we learned of Paul’s death.

I have known Laci since the 1970s. An energetic young an, he came to Britain to give an invited talk at the British Combinatorial Conference. In the Hungarian tradition, he offered prizes for solutions to some of his problems, in the only hard currency to come from the other side of the Iron Curtain, Rubik cubes (these were an exciting new invention at the time). When Akos Seress invited me to the conference, it was hard to believe that Laci could be 60. I was reassured when I saw him; he is still an energetic young man.

It was an extraordinary conference, both for the obvious affection in which Laci was held by many students and academic descendants, colleagues, collaborators and friends, and for the range and depth of the mathematics and computer science presented. And, especially, for the interconnections. Recent work on extending the results of combinatorial number theory to non-commutative situations has applications to network algorithms; the classification of finite simple groups is applied to testing completeness of sets of quantum gates.

Early on, it was clear to me that information was coming in faster than I could assimilate it. I suggested to Laci tha slides of the talks should be put on the conference web page; he passed the suggestion on to Akos, and it is being done.

My own talk was on the fourth day, just before lunch. In the morning session, I decided to add to my talk a loosely-connected “appetiser”: a puzzle about the computational complexity of finding fixed-point-free elements in permutation groups. So I wrote a couple of frames, typed them up, sent them to London, pasted them into the file, compiled it, fetched the PDF back, and put it on a memory stick. My Asus eee-pc performed flawlessly. There was no time to proof-read it, but apart from one misprint (duplicated by copy-and-paste), it was fine.

And of course, there were many mathematical and personal interactions, with friends old and new. Csaba Szabó introduced me to three of his students who are working on homogeneous structures. Robert Bailey and I had things to talk about, stemming from a long paper we wrote recently. Someone asked me a question about permutation groups; I was able to reply that the problem was solved by Laci and me twenty years ago, in a paper that we never got around to finishing.