## You're reading: Posts Tagged: Online Encyclopedia of Integer Sequences

### Integer sequence review: A010727

The Online Encyclopedia of Integer Sequences contains over 200,000 sequences. It contains classics, curios, thousands of derivatives entered purely for completeness’s sake, short sequences whose completion would be a huge mathematical achievement, and some entries which are just downright silly.

For a lark, David and I have decided to review some of the Encyclopedia’s sequences. We’ll be rating sequences on four axes: Novelty, Aesthetics, Explicability and Completeness.

#### A010727 Constant sequence: the all 7’s sequence.

7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, ...

### Towards a working definition of the terrifying numbers

Someone — it may have been Matt Parker — told the MathsJam conference last weekend there was now a terrifying number of monthly MathsJam meetups, and a murmur went around the room. It was just about the only audience in the world where more than a couple of people would have asked “how do you define a terrifying number?”

### Interesting Esoterica Summation, volume 4

Dust off your thinking hat and do some mind-stretches because here’s another course of Interesting Maths Esoterica! It’s been several months since the last volume so this is quite a big post. I won’t mind if you skim it.

In case you’re new to this: every now and then I encounter a paper or a book or an article that grabs my interest but isn’t directly useful for anything. It might be about some niche sub-sub-subtopic I’ve never heard of, or it might talk about something old from a new angle, or it might just have a funny title. I put these things in my Interesting Esoterica collection on Mendeley. And then when I’ve gathered up enough, I collect them here.