# You're reading: Main

### The OEIS now contains 300,000 integer sequences

The Online Encyclopedia of Integer Sequences just keeps on growing: at the end of last month it added its 300,000th entry.

Especially round entry numbers are set aside for particularly nice sequences to mark the passing of major milestones in the encyclopedia’s size; this time, we have four nice sequences starting at A300000. These were sequences that were originally submitted with indexes in the high 200,000s but were bumped up to get the attention associated with passing this milestone.

### Proof by sedition

$n > 2$

An unexpected bit of controversy involving mathematical notation hit the internet last week, when China's government briefly blocked all Chinese internet users from viewing any page or message containing the letter n﻿.

Apparently, those in charge of the Great Firewall feared that those who disapproved of Xi Jinping removing the two-term limit on his presidency of China would use the letter n to refer to the now-arbitrary number of terms for which he can remain in power.

There's some more context in a post by Victor Mair on Language Log, and in the Guardian.

### LMS Meeting in honour of Maryam Mirzakhani

The London Mathematical Society are organising an event later this month in honour of the late Fields Medalist Maryam Mirzakhani. It's at the University of Warwick on 22nd March, and will include talks outlining some of Mirzakhani's work, followed by a drinks reception and dinner. The event is part of a larger EPSRC symposium on Teichmüller dynamics.

More information and registration﻿

### Faces of Women in Mathematics

This is nice for International Women's Day. Filmmaker Irina Linke and mathematician ﻿Eugénie Hunsicker have put together this montage of women in maths from all around the world.

### Stanisław Ulam biopic

There's going to be a biopic of physicist/mathematician Stanisław Ulam, titled Adventures of a Mathematician﻿.

Hollywood seems to be working its way through 20th century mathematicians – off the top of my head, there have recently been biopics of John Nash, Alan Turing, Stephen Hawking and Srinivasa Ramanujan. What I want to know is, when do we get Michael Sheen playing John Horton Conway?

There's some information about Adventures of a Mathematician, starring Jakub Gierszal as Ulam, at ScreenDaily.

via MathFeed on Twitter.

### Approaching Fermi problems with the approximate geometric mean

I gave a talk on Fermi problems and a method for approaching them using the approximate geometric mean at the Maths Jam gathering in 2017. This post is a write up of that talk with some extras added in from useful discussion afterwards.

Enrico Fermi apparently had a knack for making rough estimates with very little data. Fermi problems are problems which ask for estimations for which very little data is available. Some standard Fermi problems:

• How many piano tuners are there in New York City?
• How many hairs are there on a bear?
• How many miles does a person walk in a lifetime?
• How many people in the world are talking on their mobile phones right now?

Hopefully you get the idea. These are problems for which little data is available, but for which intelligent guesses can be made. I have used problems of this type with students as an exercise in estimation and making assumptions. Inspired by a tweet from Alison Kiddle, I have set these up as a comparison of which is bigger from two unknowable things. Are there more cats in Sheffield or train carriages passing through Sheffield station every day? That sort of thing.

### Review: Closing the Gap, by Vicky Neale

Did you read Cédric Villani’s Birth of a Theorem? Did you have the same reaction as me, that all of the mentions of the technical details were incredibly impressive, doubtless meaningful to those in the know, but ultimately unenlightening?

Writing about maths, especially deep technical maths, so that a reader can follow along with it is hard – the Venn diagram of the set of people who can write clearly and the set of people who understand the maths, two relatively small sets, has a yet smaller intersection.