Here's how the loot table functions:
When a husk dies, there is a 50% chance a block of sand will drop.
For each level of Looting, there a roll, with a 25% of success that you will get a block of sand.
The best way to visualize it is that when you kill a husk, you flip one coin, and roll a 4 sided die for each level of Looting you have on your weapon.
Now count the total amount of both Heads and Fours you get and that will equal the amount of sand you will receive.
Probabilities of getting sand from husks at different levels of looting:
No Looting
0: 50%
1: 50%
Average Sand/Kill: 0.5
Looting I
0: 37.5%
1: 50%
2: 12.5%
Average Sand/Kill: 0.75
Looting II
0: 28.125%
1: 46.875%
2: 21.875%
3: 3.125%
Average Sand/Kill: 1
Looting III
0: 21.09375%
1: 42.1875%
2: 28.125%
3: 7.8125%
4: 0.78125%
Average Sand/Kill: 1.25
There are other data packs out there that make husks drop sand, but the ones that I found didn't feel very balanced IMO so I decided I'd make my own.