Z_16 S={+-3,+-5,8}: n=16 d=5 tau(0)=4.267766953 tau(399/400)=4.995518583
     local max near p=91/400 (0.2275): tau=5.68346294799
     local min near p=13/16 (0.8125): tau=4.81074482689
Z_21 S={+-2,+-7,+-9}: n=21 d=6 tau(0)=3.983955833 tau(399/400)=5.997378596
     local max near p=41/100 (0.4100): tau=5.92294165428
     local min near p=29/40 (0.7250): tau=5.85421099766
done
