My four-year-old son has declared 36 to be the best number. Archived at: https://www.jeremykun.com/shortform/2025-02-23-1057/ - ThreadSky

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jeremykun.com • 8 days ago

My four-year-old son has declared 36 to be the best number.

Archived at: https://www.jeremykun.com/shortform/2025-02-23-1057/

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jeremykun.com•8 days ago

His reason: 36 is the only number (he knows of) that is both a square and a staircase number AND an up-and-down-staircase number.

jeremykun.com•8 days ago

"Staircase numbers" are what he calls triangular numbers (numbers that are the sum of the first \(n\) integers). This name comes from the blocks he has that can be arranged into a staircase. He also calls them "step squad" numbers thanks to Numberblocks.

jeremykun.com•8 days ago

An up-and-down-staircase number is a sum of two sequential triangular numbers, representing the up and down parts of the staircase. He also knows that all squares are up-and-down-staircase numbers, though that doesn't make 36 any less amazing.

jeremykun.com•8 days ago

The next square triangular number is 1225 (OEIS A001110 (https://oeis.org/A001110)), so I doubt he will notice 36's non-uniqueness for some time.

jeremykun.com•8 days ago

The next natural question is, "What the hell is a four year old doing identifying triangular squares?"

jeremykun.com•8 days ago

Despite my wife and I both having math degrees, and our willingness to engage with him when he shows interest in math, we basically didn't do anything to actively foster this behavior. We let him watch Numberblocks (https://www.youtube.com/channel/UCPlwvN0w4qFSP1FllALB92w) (30 minutes per day),

isibel.bsky.social•8 days ago

Maybe more convincing than 4 for 2*2=4, 2+2=4, 2^2=4 very cool :)

jeremykun.com•8 days ago

I tried briefly to explain powers to him but I don't think he quite gets it. Then again, he gets that multiplying powers converts to adding the exponents so... 🤷‍♂️

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