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… Continue reading Foresight
Author: Evan Chen (陳誼廷)
Evan is a math olympiad coach who completed his number theory PhD at MIT.
USEMO 2025 announcement
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… Continue reading USEMO 2025 announcement
How to make the most out of MOP
I had a student at MOP ask me something equivalent to “how should I study while at MOP?”1 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… Continue reading How to make the most out of MOP
Thoughts on teaching multivariable calculus
In my last semester of MIT I led a recitation (i.e. twice-a-week review) session1 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… Continue reading Thoughts on teaching multivariable calculus
IMO 2024 and 2025
I was a coordinator for last year’s IMO 2024 and this year’s IMO 2025.1 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:… Continue reading IMO 2024 and 2025
2011 N1 = 2024 A2
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 $latex {d > 0}&fg=000000$, let $latex {f(d)}&fg=000000$ be the smallest positive… Continue reading 2011 N1 = 2024 A2
A stupid “real-life” application of quadratic reciprocity
The application During this year’s MOP, we used the following procedure to divide some of our students into two classes: Let $latex {p = 7075374838595186541578161}&fg=000000$ 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 $latex {s}&fg=000000$.… Continue reading A stupid “real-life” application of quadratic reciprocity
OTIS XI Applications Out
OTIS 2025-2026 applications are due August 1, 2025. The usual fare. https://web.evanchen.cc/otis.html#apply
Words Spent
One of my favorite Djikstra programming quotes is about thinking via “lines of code spent” rather than “lines of code produced”. I started using this as a philosophy in my writing too: words spent. Background One of the things that’s surprised me about student writing is how poorly words are spent. You’ll have a solution… Continue reading Words Spent
Teammate Hunt 2025 Author Notes
Thanks to Olga and Holly for factchecking a draft of this post. Remaining errors are my responsibility of course. The recent 2025 Teammate Hunt just finished, which went really well. See the link to the wrapup. I was a minor supporting character in the organizing team, mostly just taking care of writing a few puzzles… Continue reading Teammate Hunt 2025 Author Notes
Power Overwhelming 