I am going to break it down.

Let's say you get it at the 1000 Seals:

1 Fragment per 60 pulls = 16.6 Fragments

2 Fragments per 60 = 33.3 Fragments

1.5 Fragments(Average it out) = 24.9 Fragments

Now if it takes 1300 Seals

1 Fragment per 60 pulls = 21.6 Fragments

2 Fragments per 60 = 43.3 Fragments

1.5 Fragments(Average it out) = 32.5 Fragments

Ranging between 16.6 - 43.3 Fragments based on RNG.

So the mean would be around 29.95 based on all the variations.

This is just an estimated value as I do not know the exact rates hashirama's fragment drops.