A400000 Winners

I allowed myself to edit the title slightly, to hopefully make it more clear to people familiar with OEIS - it was a celebratory contest to determine which sequence should be the 400'000th entry in the database.

This might be skirting the topicality guidelines a bit, but I think we've had enough OEIS-adjacent things posted here to justify this. Even if you don't find the contest sequences particularly interesting, hopefully you'll still think that this milestone is worth celebrating? :)

Understanding the winning sequence took me a moment - Sloane's drawing and the listed example for n=8 are helpful. I still don't understand the justification of why this sequence contains every natural number; hopefully I'll get it when I look at this at a more reasonable hour.