Truth

It’s the supply cap equation. “The total supply of Bitcoin is calculated by summing the issuance across 33 reward eras (from the genesis block through the 32nd halving). Each era lasts 210,000 blocks—roughly four years. In each era, miners receive a block reward that starts at 50 bitcoins and...

Or literally: “The sum from i equals zero to thirty-two of two hundred ten thousand times fifty over two to the i equals twenty-one million."

It’s interesting to note that this derivation was parsed out by developers and economists analyzing the protocol parameters from the code and the whitepaper. It is not in Satoshi Nakamoto’s original 9-page paper.