I was on the A340 from FRA last week and I think they have power in Y class, the seating is 2 4 2 and I would guess you would be best to get a 2 row to be sure your not fighting for a socket.

One thing I have learnt is this. Make sure you have a selection of plugs as they dont all work. I ended up using a flat type rather than the round type to get power. I also know that when you plug in take out your battery first, once its working then you can put the battery in if you need to charge it but be careful as it may trip the socket, which should reset itself after 20 seconds. I know this sounds strange but for my laptop I have a UK 3 flat pin plug and also a spare cable/plug that runs into the transformer that is Taiwan/USA flat blade plug. Sometime it works if I take the flat blade and put that into a travel plug with round pin. IT is a real lottery on planes using the power and I also think it depends on how many people are using the power as well.