Incrementing numbers in dynamic rows

I have a form which has dynamic rows, added by clicking an add button. What I would like to do, is to have a column that has a row number, starting with 1, which increments up when a new row is added, but also would increment down if a row was deleted.

It is set up to be able to delete any row, so any number above a deleted row would need to increment down one, while obviously the ones below would stay the same.

Just for clarity sake, if I add rows to have 5, numbered 1 to 5, and row 3 is deleted, rows 4 and 5 would need to increment down one while rows 1 and 2 would remain the same. The end result is that the rows are always numbered in sequential order.

Thanks