Square layers make the growth visible. The book renders a finite grid of exact integer rows, not a smooth curve.
highlighted = computed this step
A finite exact grid
For a square layer with d inputs and d outputs, the count is d times d plus one. The table samples only explicit integer sizes; it is not a smooth curve.
params(d)=d(d+1)
The counts jump
At d=2 the count is 6. At d=4 it is 20. At d=8 it is 72. At d=16 it is 272.
2↦6,4↦20,8↦72,16↦272
The larger rows
The same exact formula gives 10100 at d=100 and 1001000 at d=1000. These are still exact integer rows, not interpolated values.