## 24 Oct Carnival of Mathematics 139

Hello! We are pleased to present before you the 139th Carnival of Mathematics, a round up of a month’s interesting stuff from the blog-sphere. The last carnival was hosted by Yen Duong at Baking and Math. Before we get into the stuff that people submitted for this carnival, let me mention some of the nice things about the number 139. The very first thing that is interesting about this one is that, it is a prime number and not just any prime number; it is a twin prime with 137. This itself justifies the number to be very very interesting, as twin primes are very rare to find. This makes 139, a very happy number as well. 🙂 *(Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number either equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers, while those that do not end in 1 are unhappy numbers (or sad numbers).) *We could go on and on about 139 for a long time, OEIS itself has over 8000 sequences where this number appears, so let us just mention the stuff we got for this carnival.

- The first submission is by Thomas Lang, which is quite interesting. Have you seen a set of equations which you can plot and get your favourite image back? How do you do the reverse procedure. This interesting post does the reverse plotting of the redditlady and redditdog.
- Chances are very high that you have lost something valuable, and had to go to a lot of trouble in figuring out how to get the things back, where did you lose it? If only, Google could look for lost stuff as well! There is interesting mathematics involved in this too, and the next submission by Timothy Revell discusses exactly this. This is also a part of a new book that Timothy is writing.
- Moving on, let’s talk about birthdays. How many people do you need in a room to have two people with the same birth month? Yes, the answer is pretty simple: 13. What about the same date? Still simple enough: 367. But what would be the maximum number of people present in a room with no overlap of birthdates? A short blog post discusses this, can you do better than the post author?
- Like the rest of the world, perhaps you are also worrying about the Brexit and its repercussions. However, do you feel the data that has been portrayed makes sense to you? Bob Taylor has an interesting account of Brexit via maps, which is definitely worth a read.
- Manan Shah has submitted his post titled Does 11=8+3?, which is an interesting take on how mathematics can be ‘spoken’, if it were a language. This provides some thought for teachers as well as people interested in mathematics education.
- Do you like taffy? I sure do, but I had no idea that mathematics can go into the making of a perfect taffy. In an interesting post about this, Evelyn Lamb describes how topological dynamics comes into play while pulling taffy. The post has a good description of the taffy pulling machine with historical nuggets and makes for a ‘sweet’ read.

That’s all from this Carnival, and thanks a lot for all the submissions. The next Carnival will be hosted by Tom at Mathematics and Coding.

Download this post as PDF (will not include images and mathematical symbols).

Managing Editor of the English Section, Gonit Sora and Research Fellow, Faculty of Mathematics, University of Vienna.

## Thomas Lang

Posted at 10:17h, 26 OctoberWow. Thanks so much. Glad you like the uncanny use of technology! Oh, the birthday problems are a classic. The fun part is that they can be experimentally verified in casual settings. 🙂

## Gonit Sora

Posted at 14:48h, 14 NovemberHi Thomas, thanks for dropping by. We enjoyed your post. Keep them coming. 🙂