Independently constructed eight-point plane cubic pencil 1005a6f72cab52f0 at t=-114/1709. Rank exactly 16: exact local 2-descent characters certify 16 independent rational points, and unconditional PARI algebraic 2-descent gives upper bound 16. The displayed quadratic base change embeds the curve in the independently derived K3 family recorded in companion metadata.
Andrii Prokhorenkov ·