Triangle of numbers of partitions of n with total number of odd parts equal to k from {0,...,n}.

Triangle T(n,d) read by rows: Number of ascent sequences of length n with d zeros.

I'm not sure I can explain it, but this is @motivickyle.bsky.social.

Triangle read by rows: T(n,k) is the number of Grand Dyck paths of semilength n that have k double rises above the x-axis (n >= 1, k >= 0).

Hey! That’s the one in the profile picture!

Number T(n,k) of entries in the k-th cycles of all permutations of [n] when cycles are ordered by decreasing lengths (and increasing smallest elements); triangle T(n,k), n>=1, 1<=k<=n, read by rows.

"Did you know..." section of wikipedia homepage

Did you know... PMP made the front page of Wikipedia?

Thank you, @wikipedia.org. We're thrilled to be featured in the "Did you know..." section on Pi Day.

Happy Pi Day! 🥧🎉

Students' favorite Abstract Algebra problems A collection of students' favorite problems from my fall 2022 Introduction to Abstract Algebra I class.

Lately, I've been assigning my upper division math students "Choice Exercises" as a part of their homework assignments, where they get to choose from several options.

When I taught Abstract Algebra in fall 2024, I asked students to say which problem was their favorite, which I've recorded here.

#HMC #ComputerScience professor Lucas Bang has received the 2025 Undergraduate Research Faculty Mentoring Award from the #CRA Education Committee for his exceptional work with undergraduate students including mentorship, research and graduate school guidance. Read more at uqr.to/lb-cra.

The US Is Counting Traffic Deaths Wrong By emphasizing the number of people killed per mile rather than deaths per capita, traffic safety groups risk normalizing the factors that make American roads so deadly.

Given reports that Americans buy SUVs in part because the other cars on the road are big, it surprised me that "The likelihood that someone gets into a fatal collision while traveling to and from work [is] higher if they drive a heavy SUV or pickup truck with big blind spots instead of a […] sedan."

The number of non-equivalent distinguishing coloring partitions of the path on n vertices (n>=1) with exactly k parts (k>=1). Regular triangle read by rows: the rows are indexed by n, the number of vertices of the path, and the columns are indexed by k, the number of parts.

I love this! It inspires me to start playing with these ideas again!

Check out @fdecomite.bsky.social’s incredible shelf based on Squaring the Square!

I did! Just got a 3D printer a few days ago!

I designed them in OpenSCAD and customized them for some 3mm x 1mm magnets that I bought for about 3¢ each (purchased on Amazon, for better or worse.)

I'll try to write a blog post about it soon, but reach out in the meantime if you want the files.

And a third stellation of a rhombic dodecahedron!

And his stellation!

Check out Robin's version of a rhombic dodecahedron!

Inspired by @robinhouston.mathstodon.xyz.ap.brid.gy's G4G16 gift of tetragonal disphenoidal blocks, I've made some magnetized versions, which are satisfyingly click-y!

Triangle read by rows: T(n,k) = number of step shifted (decimated) sequence structures of length n using exactly k different symbols.

Pentagonal icositetrahedron puzzle A puzzle on the faces of the pentagonal icositetrahedron with 3D models, STL files, photos, and video illustrations

You can read more about the puzzle here.

That's right! This is a puzzle on the faces of the pentagonal icositetrahedron, which has three short edges and two long edges.

G4G16 Gift Exchange The gift I made for Gathering 4 Gardner in 2026, together with files so you can make more at home.

I wrote a blog post about my G4G16 gift. If you want a copy of your own, download and print the files!

The photo shows identical soft cell units assembled into a lattice structure. The shape seems to have the same qualities as a truncated octahedron, It won’t dense pack as efficient as the Kelvin or Weaire-Phelan structures because the deformation of the faces increases the surface area of the individual units and makes the ratio of the volume of the object to the edge length less efficient. But it looks pretty and I’m working on filling in the holes now .

Enlarging 3D printed models. I am imagining the structure of our physical universe just above the Planck scale, where quantum forces overcome the force of gravity. If you are exploring the fundamental structure of three dimensional form, this is the place to be!

Petition: Christopher Havens is an inmate in the Washington state prison system who has been collaborating on mathematics with people both inside and outside prison. He was recommended for clemency by the parole board. However, governor Bob Ferguson has not granted it yet. (link below)

Potato printing plot party postcards A postcard designed for the 2025 plotter postcard exchange #ptpx based on 'Potato Printing,' a game that M.C. Escher played with his kids.

Peter has a nice blog post about making his card. Check it out peterkagey.com/blog/2025/12...

I got some nice #ptpx cards in the mail today. Thanks @peterkagey.com @aotearoan!

Three podcasts that I loved that have since stopped releasing new episodes, but which I wish more people knew about.

– Hakai Magazine Audio Edition
– Ox Tales (by the Oxford Symposium on Food and Cookery)
– 70 Over 70 (by Pineapple Street Studios)

Please recommend defunct podcasts to me too!

I still do it, but they’re very low stakes—hardly worth more than a homework assignment.

A video of the pen plotter in action!

Potato printing plot party postcards A postcard designed for the 2025 plotter postcard exchange #ptpx based on 'Potato Printing,' a game that M.C. Escher played with his kids.

I wrote about the postcard I designed for the 2025 plotter postcard exchange #ptpx on my blog, based on a potato-based game that M.C. Escher used to play with his kids.