| $<0.90304$ | [YC2023] | Latest computer-aided proof that significantly lowers the upper bound. Uses numerical integration and search over tour patterns. |tracked since 2026-07-24 — no movement seen yet
Lower bound, last-listed row
| $0.6277$ | [GJ2020] | Improved rigorous lower bound using an approach based on nearest-neighbor distances, correcting and tightening a prior argument of [S2015]. |tracked since 2026-07-24 — no movement seen yet
Cite this rowBounds Ledger — The Beardwood–Halton–Hammersley constant (12a)
upper bound: $<0.90304$ (tracked since 2026-07-24 — no movement seen yet)
lower bound: $0.6277$ (tracked since 2026-07-24 — no movement seen yet)
Mirrored from teorth/optimizationproblems@2c1968c. These are the last-listed rows of that constant's bounds table — a listing position, not a statement that this bound is the strongest or most recent. A snapshot at that sha, not a live read.
https://u00dxk2.github.io/bounds-ledger/c/12a.html