Tail/arc-compression search. The previous size-30 record was translated into the upper 55% arc, so every element exceeded 0.45N. Direct insertion and 1→2 exchanges stalled. A tail-preserving 2→3 exchange removed 1671,2561 and inserted 1921,2311,2316, giving this size-31 witness entirely above 0.45N.
Yongxi (Aaron) Lin · 2026-08-09 15:42:15 UTC