## Sunday, March 28, 2021

### Playful Math Carnival 145

Welcome to the 145th edition of the Playful Math Carnival. Once known as the Math Teachers at Play Carnival, this edition follows the Denise Gaskins' (founder of this here carnival) blowout 144th Anniversary Edition, as night doth follow gentle day, and by that we were blown away.

Sadly, there's nothing interesting about the pentagonal semiprime 145. Well, besides 145=1!+4!+5!. There are only four numbers for which that's true.  And it's the fourth number that's a sum of squares in two different ways. And it's a Leyland number, because 3^4+4^3=145. (I wonder what the next Leyland numbers before and after are?) And the 145th prime number is 829 and 145829 is prime and the largest prime factor of 145 is 1+4+5+8+2+9 and that 145 is congruent to 1 in mod 8, mod 2, and mod 9. But besides that...  there's practically nothing. (All these are from Pat Bellew's fun number site.) And 145 shows up in Matt Parker's melancoil. 145 degrees (F) makes something medium rare...  maybe that should be the goal for this edition?

 Volvo 145. Ove approved.

Hop in the 145 and let's go!

Books & Essays

Just before this month started I got to participate in a nifty mathzine fest from Becky Warren, Chris Nho and Ayliean. Technically February, it was after Denise's edition so I'm counting it. Several of the results are on the Public Math website, which has more besides. Also see the mathszine hashtag on Twitter.

That was my introduction to Ayliean, who had some thoughts on STEMinism.

Some of those zines inspired Sophia Wood for her first Fractal Kitty zine, on the Cantor Set.

Jim Propp was musing on division by zero. History, what ifs, new possible numbers...

Edmund Harriss has a new children's book out, HELLO NUMBERS! What Can You Do? and has been out supporting the release. Read more at Chalkdust's Math Book of the Year series. Also super curious about Eugenia Cheng's Molly and the Mathematical Mystery.

Speaking of playful math authors, RIP to Norton Juster, author of The Phantom Tollbooth and The Dot and the Line.

Games

Sarah Carter reviewed the mathgame Proof positively.

James Cleveland posted his new linear graphing mathgame. Played it with my games seminar students and I think there's a lot of potential.

Simon Gregg and his learners were making variations on Snakes and Ladders.

Henry Segerman suggests this negatively curved sliding puzzle.

Excellent post at Play and PK on Listening.  Guest appearance from the always welcome Max Ray Riek in that post.

I've been making some GeoGebra for remote learning play. There's a measure division game, a fraction comparison game, a fraction addition/iteration/equivalence game and the classic Shut the Box.

Art

Dana Ernst shared quilts his student Michelle Reagan made on the 5 groups of order 8.

Practically a quilt, Master of the Pattern Blocks, Hana Murray, made this amazing tiling replete with dodecagons.

Robert Fathauer was interviewed on Math, Art and Tessellations. His new book is a masterwork.

Sophia is also in the middle of a 101 days of coding challenge, and shared her ecliptic ripples.

Paula Beardell Krieg had some practical advice for cutting curves by cutting straight.

I got to work on a fun project with my son studying art education, Yemeni squares

Wait There's More

I found this perusing old NCTM practitioner journals for fraction tasks and it sparked some interesting conversation. Like just how many solutions are there?

And it wasn't the only time 1/3 appeared in this third month, as I saw a nifty Roger Nelson proof with out words of an odd identity.

Iva Sallay is hosting the next Playful Math Carnival, 146. It's sure to be a treat, as she is a prodigious puzzle poster herself (take these Easter season Egg Puzzles, for example), and found several possibilities for this edition!

I enjoy putting these together, even though I am not regularly blogging myself. (Despite my best intentions...) One of the reasons I started blogging was to share and curate some of the cool things I was seeing from the amazing MTBoS, and it's still a good thing. If you're interested in hosting, just let Denise know.

NPR made a comic of this teacher's pandemic teaching story. (Less helpful, probably, McSweeney's suggestions for teacher self-care.) Hope you are taking care of you and yours, and getting vaccinated!

So long 145! Hope it was 5x5.