The following diagram shows the relationship between the entries of the seq command and the summation symbol:
The last 1 in the command indicates the step size. [We use a step size of 1 to indicate that x increases by 1 in each step.]
The result of this command is a list:
You should compare this list with the summands listed above. Unfortunately, this list is too long to appear on the screen on the calculator. Use the right and left arrow keys on the calculator to view the list.
The sum command adds up the elements of a list.