The Ford–Johnson algorithm, no longer unbeaten for less than 47 elements

Paper, complete comparison trees, and Lean 4 formalisation proving that 26 elements can be sorted in at most 90 comparisons and 46 elements in at most 194 comparisons. The one-comparison saving over Ford–Johnson extends throughout 26–32 and 46–64 elements. The code, scripts, and certificate data are licensed under Apache 2.0; the paper (note.tex and note.pdf) is licensed under CC BY 4.0.