Arnold's meanders: verified counts, paper, and film

Counting Arnold's meanders with algorithms proved correct in Lean 4.

• Paper: Counting Arnold's meanders with verified algorithms
• Film: two encodings of the same 2-minute, 1080p, 30 fps recording of the visualization (viz/index.html): the river crosses the road 0, 1, 2, … times, then races through every river up to n = 14 and sweeps to n = 32, ending on the proved count 15,012,865,733,351.
  • arnold-meanders-1080p.mp4 (36 MB), for the web
  • arnold-meanders-1080p-master.mp4 (93 MB), the high-quality master