Given the title of this blog, I've meant to do some coalescent stuff in sage for a while. Now that I am about to teach about it in a class, I've finally found the motivation:
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjYzkBb0osKeJtZKF3zgq4XVk-pkOHYLFHHvJD05v1aj4sjokIFU0Hj_mdC_XTBuMq2CCiyo6Z5TU4Xx4tgdQ79NhQVwzk1a2o6uOohUgLWG7bterdqzoxL_qCI60atT7LStaD0f-nbcK7W/s400/coal100.png)
(It's cooler animated, but I can't figure out how to post a gif animation here.)