You are a banker. You have a set amount of coins to distribute to the population. Instead of giving it out all at once, your boss came up with this formula.

Every $\sim 4$ years, you increase the value of $i$. For a given value of $i$, this formula tells you how many coins to hand out to your customers. Because $i$ is in the denominator (the lower part of the fraction), the amount you hand out every 4 years decreases.

This turns out to be quite useful, as coins magically seem to become more and more valuable (or is the other way around, they become more valuable because of this formula? We'll never know...).

After 33 epochs of 4 years, you have handed out all coins, and their sum amounts to $\sim 21$M coins. Everyone agrees on this formula, so you can't modify it unless you manage to convince a large enough number of people to use a different formula.

Voila, you have figured out the formula for hard money.