"Ok that's a cool picture but I don't quite see the connection to the paragraOMG IT'S INTERACTIVE!" Really cool demo Fil :)

ty!

Agreed, perhaps add a small note that the map is interactive? :) (Otherwise people might miss one of the best parts) (Also, I'm hoping that someone might create a fork where all connections are visible, sort of like a density map)

Other ideas are to color each number with its number of predecessors, and show the predecessors on hover. For performance you might also want to store the n ⇛ step(n) result in a static array.

This is very cool - thanks! You can do similar things for more digits. For five digit integers, there are three attractive cycles: {53955, 59994}, {61974, 82962, 75933, 63954}, and {62964, 71973, 83952, 74943}. And similarly for six digits: {549945}, {631764}, and {420876, 851742, 750843, 840852, 860832, 862632, 642654}, Though there's just a single attractive cycle for seven digit integers. I'm not at all sure if the basins would look nice at all but, for five or six digits, it might be interesting to shade the seeds according to which cycle the sequence lands on.