I know that an arithmetic series of n terms can be written :
a + (a+d) + (a+2d) +...+ [a+(n-1)d] but I am not sure how to write it in sigma notation, I was thinking the lower limit would start at 1 but what about the upper limit? And since the sum of the integers is increasing each time would it be (n+1)? Could a formula be written in terms of a, d and n for the sum of this series that would make sense to me? What I am trying to say is can you explain it so I can understand it. I would appreciat it, I hope this makes sense to you, I don't know if this sounds logical, I am just trying to understand sums of series.