I have the following equations: (See Figure 1) I tried summing them up in one single general formula, and I got: (See Figure 2) I'd like to know two things: 1. Is my general formula correct? Please note it does not work for A1, since for my purposes, A0 does not exist. 2. If my formula is correct, how can I make it simpler, so I can computate An by hand? Thank you very much for your help! I'm sure this is gonna be simple, but my knowledge is limited.