Trouble with symsum function

Hello,

I am currently trying to calculate a scalar using the sum of two predetermined numbers and the summation of a small operation applied to values in a column matrix. The two predetermined numbers are the ends of the matrix, but the other part of the summation is what is tripping me up. I would like to index the matrix in a general form ( as the size of the column matrix will change with different inputs. I get an error that states "Index exceeds matrix dimensions." How can I fix this, I am not sure where I am going wrong. Here is my code so far:

Answer 1

[Walter Roberson]

You can never use a symbolic variable as an index.

symsum is for finding closed form formula, not for adding a definite sequence of terms. If the number of terms is known then calculate them all in vector form and sum() the calculated elements.

[Alec Betancourt]

Thanks a lot!