How to Count n-Ary Trees How do you count rooted planar n-ary trees with a given number of leaves? Use Lagrange inversion! TeXnical Issues Sage advice on viewing this blog and posting comments thereon ...

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How do you count rooted planar n -ary trees with some number of leaves? For n = 2 this puzzle leads to the Catalan numbers. These are so fascinating that the combinatorist Richard Stanley wrote a ...

This week in our seminar on Cohomology and Computation we continued discussing the bar construction, and drew some pictures of a classic example ...

Christoph Wockel asks me to forward the following question to the n n-Café: What is a reference for a generalisation of the following canonical cocycle to higher dimensions? Thanks for any hints. My ...

The math-blogosphere is abuzz with interest in the new Math Overflow, a mathematics questions and answers site. Already we at the Café have been helped with the answer to a query on the Fourier ...

Here is a rather simple — indeed almost trivial — observation concerning open string field theory (OSFT) and deformations of CFTs, which I find interesting, but which I haven’t seen discussed anywhere ...

A while back Gina asked why computer scientists should be interested in categories. Maybe you categorical computer scientists out there have your own favorite answers to this? I’d be glad to hear them ...

Category Theory and Biology Posted by David Corfield Some of us at the Centre for Reasoning here in Kent are thinking about joining forces with a bioinformatics group. Over the years I’ve caught ...

Re: Integral Octonions (Part 12) Re: Puzzle 2, I have been told that there are nice constructions of quantum groups (nice meaning, in particular, not just by writing down generators and relations) ...

Finally we get to see James Dolan in action, talking about Geometric Representation Theory! While I’ve been focusing on examples, now we’ll start to see the general principles at work in geometric ...

We should probably focus on the mathematicians who aren’t already blogging and perhaps don’t know much about it — since the ones who do, don’t need to read the Notices to learn about the issues. What ...