 # Formatting cells in a series in Google Docs/Excel

I don’t know how to phrase this so here is what I’m trying to do: I have a series of cells that I need to increase by 50 every two cells.
So here is my data: Cell 1: 0, Cell 2: 50 (+50), Cell 3: 100 (+50), Cell 4: 200 (+100), Cell 5: 300 (+100), Cell 6: 450 (+150), Cell 7: 600 (+150), etc.
So is there a way to format the cell allowing the sequential increase to be every two cells instead of after every one? Sorry if this is confusing or not phrased well I wasn’t very sure on how to explain this. Also to anyone who takes a look at this question, thanks for your time.

If A1 is 0, then put this to A2: `=A1+50*TRUNC(ROW()/2)` and drag-copy down to A3… as required.

Another (non-recursive) formula for this series is: `=50*TRUNC(ROW()^2/4)` (where ROW() defines the Nth series member). You might calculate your 35th number as `=50*TRUNC(35^2/4)` without need to get all previous members.

Thank you so much! I really appreciate it I had no idea what so ever on how to do this so you definitely made my day!