Singular primes (legacy)

A historical list of primes with a singular realization-space fiber, stored as a string such as "[3, 13]". For simple three-lines matroids it came from an exhaustive integer-certificate calculation. Elsewhere it records the hits of a bounded prime scan and is only a lower bound, so a missing prime does not mean the fiber there is smooth.

Use rs_singular_fiber_primes when an exhaustive answer is needed. For rank 4 the column was written by scripts/rank_n_smoothness_and_singular_primes.jl, and the repository does not document its completeness there.

Full details: docs/realization_scheme_singularity_census.md (Section 18.2).