THE EIGHTEENTH GENERATION:
Serug lived for 30 years and begat Nahor.  (Genesis 11:22)
Serug lived for 200 years (230 years) after he begat Nahor and begat sons and daughters.  (Genesis 11:23)
The age of the earth was 1857 years when Nahor was born.  (Genesis 1:24-31, 5:3,6,9,12,15,18,21,25,28, 7:6,11, 9:28, 29, 11:12, 14, 16, 18, 20, 22)