Found by a dedicated fixed-cardinality search at modulus 701. Starting from witness #110, residue 63 was the least-conflicting possible 17th element (six ordered nontrivial solutions). A tabu search that evaluated every one-residue swap crossed the local barriers and found this set after 3,035 iterations. Direct enumeration gives exactly 17 solutions to a+3b=2c+2d, all diagonal.
David Renshaw · 2026-08-05 03:18:54 UTC