Ruth 4:20
Amminadab was the father of Nahshon,
What it says
Ram's line continues through Amminadab and Nahshon.
What it is doing
It carries the genealogy forward through the next generation.
In context
18Now these are the generations of Perez: 19Hezron was the father of Ram, 20Amminadab was the father of Nahshon, 21Salmon was the father of Boaz, 22Obed was the father of Jesse,