Life isn’t a straight line. Finding your dream career involves a lot of twists and turns, like a river. In my search for the perfect job, I find myself constantly changing course, because even though planning is helpful, the plans themselves are useless.

In past years, I’ve been through sailing, college consulting, and fashion design. And now I find myself eating my words from last year. Despite how much I hate New York, I’m thrilled to announce the upcoming opening of T.O.A. Asian FusionPlease forgive the slight RAS syndrome in the name. at 33 Sunrise Hwy, Merrick, NY 11566.

Here’s the press release from Newsday on the Merrick location:

T.O.A. Asian Fusion is on a roll. Four months after opening its fifth location, in East Islip, the restaurant group has announced its sixth: Evan …

Some of you have probably noticed that I’m helping with organizing a new contest and are asking what exactly this is. So far, I haven’t said much about it because so much is up-in-the-air (and that’s still true).

However, with the first few acceptances and registrations coming out, I’m going to post an FAQ and few quick thoughts of my own. Just to be clear, everything here is my own personal commentary and views and not those of my employer or OMEGA generally.

What is OMEGA?

OMEGA (Organization for Math Engagement and Growth in America) is a new 510(c)(3) whose ambitious long-term goal is to build great, robust math programs for thousands of students all across the USA (whether competition-like or not).

However, that is a pipe dream, because OMEGA is also about four months old and has a whopping four staff, many of …

Here’s a section from the H-group Hanabi strategy page:

LINES

During your turn, part of figuring out the best move involves looking into the future to see what the next player will do. If they discard, will it be okay? Is there some obvious clue that they will do? And so on.

As you get better at Hanabi, you will need to do this prediction not just for the next player, but for an entire go-around of the table. And as you really get good at Hanabi, you will need to do this for as far in the future as you can reasonably predict. (Sometimes, this means 15 moves or more in the future.)

Similar to chess, initiating a move in which you can predict the next sequence of moves is called initiating a “line”.

In post-game reviews, we will often compare and hypothetically “play through” two different lines …

Announcement for the USEMO 2025:

• The USEMO 2025 will be held on October 25 - 26, from 12:30pm - 5:00pm ET each day.
• For competitors, registration will open in early October on AoPS.
• If you’d like to volunteer for grading, the signup for that is posted on the website now too. You should sign up no later than October 25 for that.

As usual, all relevant info at https://web.evanchen.cc/usemo.html.

I had a student at MOP ask me something equivalent to “how should I study while at MOP?”There is also a question about whether you should be studying much at MOP at all — you could also spend a lot of time making new friends, for example. That’s a value judgment that I think is better left to individuals and I won’t comment on it further in this post. For those of you that don’t know, MOP is the three-week summer camp for the USA’s team to the IMO.

At first I was going to just link my FAQ. But then I thought about it a bit more, and I was surprised to find that my answer was not the same as the general how-to-study FAQ. The additional condition “while at MOP” was enough to cause me to stay up that night writing an entirely different …

In my last semester of MIT I led a recitation (i.e. twice-a-week review) sessionFor those of you that don’t know how the system works, at MIT, 18.02 is a huge class with 400 to 500 students (mostly first-years). In order to make sure students actually get the individual attention they need (impossible during lecture), the math department also places each student in a recitation section of about 20 students each, meeting twice a week for an hour each. for multivariable calculus (18.02) at MIT (although the first few weeks are all linear algebra). It’s different from many contexts I’ve taught in before; the emphasis of the class is on doing standard procedures, but the challenge is that there is a lot of ground covered. That is, compared to other settings I’ve taught, there is generally a tradeoff of less depth for more …

I was a coordinator for last year’s IMO 2024 and this year’s IMO 2025.Before, I was a coordinator for some virtual IMO during the pandemic too, which is much less fun. And from 2017-2019 I was an observer for the USA. Here’s some thoughts about that, contrasting my IMO 2019 post.

What is coordination?

For those of you that don’t know, coordination is the grading process for IMO. As I describe it in my FAQ:

Basically, the outline of the idea is: before the exam, a marking scheme (rubric) is set for each problem, to cover the typical cases of what progress will be worth what points. Then, the leaders of each country get to see the solutions of their country’s students, while there is a number of coordinators from the IMO host country for each problem. Both the coordinators and the leaders read …

I am always harping on my students to write solutions well rather than aiming for just mathematically correct, and now I have a pair of problems to illustrate why.

Shortlist 2011 N1

Here is Shortlist 2011 N1, proposed by Suhaimi Ramly:

For any integer $d > 0$, let $f(d)$ be the smallest positive integer that has exactly $d$ positive divisors (for example, $f(1)=1$, $f(5)=16,$ and $f(6)=12$). Prove that for every integer $k \geq 0$, $f(2^k)$ divides $f(2^{k+1})$.

I like this problem, so try it out if you haven’t. This is a problem …

The application

During this year’s MOP, we used the following procedure to divide some of our students into two classes:

Let $p = 7075374838595186541578161$ be prime. Take the letters in your name as it appears on the roster, convert them with A1Z26 and take the sum of cubes to get a number $s$. For example, EVANCHEN corresponds to $s = 5^3 + 22^3 + \dots + 14^3 = 16926$. Then you’re in Red 1 (room A155) if $s$ is a quadratic residue modulo $p$, and Red 2 (room A133) otherwise.

The students were understandably a bit confused why the prime was chosen. It turned out to be a prank: if you ran the calculation on the 30-ish students in this class, it was …

OTIS 2025-2026 applications are due August 1, 2025. The usual fare.

https://web.evanchen.cc/otis.html#apply