If you take a look at your laptop's keyboard, you'll notice that the top row keys have icons printed above, with "F" and a ...

There seems to be some unhappiness about Apple removing the function keys on the next MacBook Pros in lieu of a touch screen strip.

Enter your data or use an existing data. Type into the cell where you want to place the result =SERIESSUM(A2,0,2,D2:D4).