# Help in performing computation over a list [closed]

I need to compute the quotient $\frac{n-1}{\sigma(n)-n}$ over the list say $\{9,25,49,81,121,169,...\}$ where $\sigma(.)$ is the classic sum of divisor function.

I tried to use the following codes but it did not work:

((n-1)/(DivisorSigma[1,n]-n))/@\{9,25,49,81,121,169,...\}


What must be the correct code so that I can compute the stated quotient over the given list. Thanks a lot.

## closed as off-topic by happy fish, Bob Hanlon, Kuba♦Mar 9 '17 at 6:45

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "This question arises due to a simple mistake such as a trivial syntax error, incorrect capitalization, spelling mistake, or other typographical error and is unlikely to help any future visitors, or else it is easily found in the documentation." – happy fish, Bob Hanlon, Kuba
If this question can be reworded to fit the rules in the help center, please edit the question.

• you need n to be # and & at the end of the function, like in your recent question 139430... – Kuba Mar 9 '17 at 6:43
• See ref/Function and linked topics – Kuba Mar 9 '17 at 6:44
• Thanks a lot for helping me. @Kuba – Jr Antalan Mar 9 '17 at 9:34

(*1*)