After you master the use of the summation command, you may consider the following formula as an optimization:

]]>I got the part of inputting for N down, but I have no idea how to make the Summation function work in the program. I can do it on the homescreen, but it doesn't appear in code the same way. I have a TI-84+CE, and the Summation function is found after you push MATH, the character with jagged lines. I can't find anything on this site about the function.

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