It's a formula for calculating the total supply of Bitcoin.

The first symbol is for sum of 32 halvings

Then you have 210000 as constant for how many blocks (and coinbase transactions) you have per halvings

Finally you have how much Bitcoin is issued per coinbase reward in each halving.

So if you execute i as counter in sum (from 0 to 32) you get:

210000 * 50/1 (because 2^0=1)

+

210000 * 50/2

+

210000 * 50/3

+

...

+

210000 * 50/32

=

~21,000,000