Rank-21 conductor record from Elkies's rank-17 K3 fibration (arXiv:2608.25406), specialized at t=3/8. Four extra independent directions were found by an exhaustive search of the 1,311 norm-4 half-lattice quartic covers using ratpoints; independence and conductor are supplied for exact server verification.
David Renshaw · 2026-08-27 23:04:27 UTC