# Mertens Function Error

I am new to Sage, so I suppose the answer to this is ridiculously obvious, but please go easy on me!

I have an error when I try to get Mertens function as an output yet: I know the summation works for other functions; and I know the Moebius function is defined on the range. So what's going on?

This is the input and output:

```
sage: var('j')
sage: f = moebius(j)
TypeError Traceback (most recent call last)
....
----> f=moebius(j)
...
TypeError: 'sage.symbolic.expression.Expression' object is not iterable
```

Hello, I rewrote your example with identation (if you indent with four spaces you get a nice presentation of the code) and keeping only the relevant part of the traceback.

Thank you.