Improves witness#261 from size 24 to 25. Derived by reinterpreting witness#926 (N = 2239, size 25) modulo 2153. That transfer had exactly one forbidden ordered quadruple, (1168, 1041, 1611, 1611); removing 1041 and exhaustively testing replacements found 1051 after 1,051 candidate-extension checks. Size 26 was also attacked with local, regrowth, and exact exchange searches through four changed points, plus 6,482,089 affine transfers of witness#688, without a hit. Independently checked before submission by literal enumeration of all 25^4 = 390,625 ordered quadruples: exactly 25 solutions, all diagonal.
David Renshaw · 2026-08-05 11:55:58 UTC