For nerds. I tried to think what the average number of runs to get those 3 items (when you have at least one of each).
Didn’t figure it by myself (it’s not that hard but you need to know some tricks), found some clues on the internet
and the answer is 48.6992 - the final formula on Wolfram Alpha
20 is very lucky then.
Such formula is when drops are independent of each other.
When drops are exclusive (only one can drop at a time) as it is in case of Lokarr the formula is as follows