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Blue

@justblue.bsky.social

Trigonographer, hedronometer, mathy maker. Advisor (and former Exhibit Concept Developer) for the Seattle Universal Math Museum. mathy t-shirts & posters: https://tricochet.com

Seeking mathy employment. Need a diagrammist? TeX-fier? Ideator?

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Blue

@justblue.bsky.social

12.13.25: Happy Plus-Equals Day! #MathyDay

I'll take the opportunity to slip-in another #ShamelessPlug for my Mathy 2026 t-shirt, available at my Etsy shop: inspiredbymath.etsy.com

Happy Plus-Equals Day! 12 plus 13 equals 25

December 13, 2025 at 4:48 PM

Blue

@justblue.bsky.social

Happy #ShamelessPlug Day!

I've added "Mathy 2026" t-shirts to my Etsy shop.

inspiredbymath.etsy.com

The back lists over forty mathy dates (in MDY format ... sorry DMY-ers!). Buy one of these, and you can ignore my #MathyDay posts for a full year.

Thanks for your support! :)

Mathy 2026 t-shirt back, listing lots of mathy dates throughout the year

November 26, 2025 at 11:13 AM

Blue

@justblue.bsky.social

11.23: Happy Fibonacci Day! #MathyDay

Happy Fibonacci Day! The Fibonacci sequence begins 1, 1, 2, 3, then 5, 8, 13 ...

November 23, 2025 at 10:57 AM

Blue

@justblue.bsky.social

11.18.25: Happy Arithmetic Progression Day! #MathyDay

Happy Arithmetic Progression Day! 11 plus 7 is 18, and 18 plus 7 is 25

November 18, 2025 at 6:17 AM

Blue

@justblue.bsky.social

For when My Dear Aunt Sally enlists in Starfleet.

via my Etsy shop: inspiredbymath.etsy.com

Closeup of a blue t-shirt featuring the insignia of the Addition, Subtraction, and Multiplication Division

Male and female models wearing red t-shirts featuring the insignia of the Addition, Subtraction, and Multiplication Division

Closeup of a black t-shirt featuring the insignia of the Addition, Subtraction, and Multiplication Division

November 16, 2025 at 1:33 PM

Blue

@justblue.bsky.social

11.14:25: Happy Plus-Equals Day! #MathyDay

Happy Plus-Equals Day! 11 plus 14 equals 25

November 14, 2025 at 2:36 PM

Blue

@justblue.bsky.social

Happy #ShamelessPlug Day!

If you like my triggy math-o-lantern t-shirt, then you might want to order one in the next day or two for delivery by Halloween. (In my experience, delivery takes about a week, but holiday shipping could cause delays.)

inspiredbymath.etsy.com

Thanks for your support! :)

October 15, 2025 at 8:41 PM

Blue

@justblue.bsky.social

10.15.25: Happy Plus-Equals Day! #MathyDay

Happy Plus-Equals Day! 10 plus 15 equals 25

October 15, 2025 at 4:47 PM

Blue

@justblue.bsky.social

9.25.25: Happy Squares Day! #MathyDay

Happy Squares Day! 9, 25, and 2025 are all perfect squares.

September 25, 2025 at 1:33 PM

Blue

@justblue.bsky.social

Happy #ShamelessPlug Day!

I've added a triggy #Halloween t-shirt to my Etsy shop

I'll also mention my design for fans of the Oxford/Harvard/serial comma. Pi-Tau COEXIST, Kangleroo, & more available

inspiredbymath.etsy.com

Thanks for your support! (This is my only source of income at the moment.)

T-shirt with a "Trig = Treat!" Halloween design with a trigonometric jack-o-lantern design.

Detail of the "Trig = Treat" jack-o-lantern design, with 30-60-90 and 45-45-90 right triangle eyes, an equilateral triangle nose, and a sinusoidal mouth.

T-shirt advocating use of the Oxford/Harvard/serial comma, The design simply shows two commas, an ampersand, and an exclamation point for emphasis.

September 24, 2025 at 6:16 PM

Blue

@justblue.bsky.social

9.17.25: Happy Arithmetic Progression Day! #MathyDay

Happy Arithmetic Progression Day! 9 plus 8 is 17, and 17 plus 8 is 25.

September 17, 2025 at 10:01 AM

Blue

@justblue.bsky.social

9.16.25: Happy Plus-Equals Squares Day! #MathyDay

Happy Plus-Equals Squares Day! 9 + 16 = 25, and all three numbers are squares. We can arrange geometric squares on the edges of a 3-4-5 right triangle.

September 16, 2025 at 8:56 AM

Blue

@justblue.bsky.social

9.9.(20)25: Happy Squares Day! #MathyDay

Happy Squares Day! 9, 9, 25, and 2025 are all perfect squares

September 9, 2025 at 1:23 PM

Blue

@justblue.bsky.social

9.4.(20)25: Happy Squares Day! #MathyDay

Happy Squares Day! 9, 4, and both 2025 and 25, are all perfect squares

September 4, 2025 at 11:25 AM

Blue

@justblue.bsky.social

9.1.(20)25: Happy Squares Day! #MathyDay

Happy Squares Day! 9, 1, and both 25 and 2025 are squares

September 1, 2025 at 12:09 PM

Blue

@justblue.bsky.social

8.17.25 (belated): Happy Plus-Equals Day! #MathyDay

Happy Plus-Equals Day! 8 plus 17 equals 25

August 18, 2025 at 7:08 PM

Blue

@justblue.bsky.social

Happy Plus-Equals Day! #MathyDay

Happy Plus-Equals Day! 7 plus 18 equals 25.

July 18, 2025 at 1:01 PM

Blue

@justblue.bsky.social

(belated) 7.16.25: Happy Arithmetic Progression Day! #MathyDay

(This is how you know that I'm not a bot.)

Happy Arithmetic Progression Day! 7 plus 9 is 16, and 16 plus 9 is 25.

July 18, 2025 at 1:00 PM

Blue

@justblue.bsky.social

Finally, a #ShamelessPlug :

My pi-and-tau t-shirts are available in the InspiredByMath Etsy shop.

inspiredbymath.etsy.com

(BTW: Etsy is currently reimbursing sellers a bit on sales made through the link; this doesn't help *you*, but *I* could use the extra buck! :)

Thanks for your support!

June 28, 2025 at 9:58 AM

Blue

@justblue.bsky.social

While I'm at it ... Since division is better as an operation than a motivation, here's a quick musical PSA advocating against pi-vs-tau tribalism. (Apologies to Billy Preston.) #PiDay #TauDay

June 28, 2025 at 9:55 AM

Blue

@justblue.bsky.social

6.28: Happy #TauDay! #MathyDay

Here's a #digitalditty to mark the occasion.

(Apologies to the Bay City Rollers)

June 28, 2025 at 9:54 AM

Blue

@justblue.bsky.social

6.19.25: Happy Plus-Equals Day! #MathyDay

June 19, 2025 at 12:46 PM

Blue

@justblue.bsky.social

Happy Shameless Plug Day! ... With #TauDay (6.28) just a month away, I thought I'd mention my tau-and-pi t-shirts. (Remember: There's room on the number line for both values, so let's stop with the belligerence!) See my InspiredByMath shop on Etsy.

inspiredbymath.etsy.com

Thanks for your support!