$ seq -f 'obase=16; =10; %g' 0 15 | bc | awk '{print $1, "0", "0"}' | svgo [ circle cx=100 cy=100 fill='#$1$2$3' r=100 ] -ino 'out_$nr.svg'
$ convert -resize 200x200 out*.svg anim4.gif https://t.co/g6higcxatp