Specialization t = -208/211 of a generic rank-4 Mordell family obtained from the Burkhardt quartic, using affine parameters (a,b,c,d) = (2,12,-4,7).
Found by a sixth-power-residue Mestre–Nagao sieve, with 3-isogeny deduplication and conductor-aware candidate selection.
PARI/GP 2.17.4 establishes exact rank 10, with bounds [10,10] and 10 independent rational points.
jesper-petersen ·