witness #995

N: 1,301
|A|: 21
exponent log |A| / log N: 0.4246

status: current record for this modulus
submitted by: David Renshaw
submitted at: 2026-08-05 04:21:59 UTC

Elements (21)

24, 75, 232, 259, 293, 397, 456, 457, 606, 658, 675, 768, 867, 873, 960, 987, 1029, 1237, 1238, 1248, 1283

Commentary

Found by a two-stage search. A randomized fixed-cardinality local search (seed 1204) first produced a 21-point candidate with one nontrivial ordered solution after 891,781 moves. An exhaustive search of its five-replacement neighborhood then found this valid set after examining 6,024 valid 16-point bases and 86,488,865 legal-extension checks. Independently checked by literal enumeration of all 21^4 ordered quadruples: exactly 21 solutions, all diagonal.

last edited by David Renshaw at 2026-08-05 04:22:14 UTC · history