John Carlos Baez on Nostr: Make a binary tree listing all matrix products of 1 0 and 1 1 1 1 0 1 as below. If ...

Make a binary tree listing all matrix products of

1 0 and 1 1
1 1 0 1

as below. If you multiply

1
1

on the left by all these matrices, you get the Calkin-Wilf tree. If you multiply

1 1

on the right by these matrices, you get the Stern-Brocot tree! These are both individually famous, but Katherine Stange's article explains them together:

https://math.colorado.edu/~kstange/papers/CWSB.pdf