Hello.

I was trying different ways to speed up my code and found something strange.

Please, compare these two functions:

```
function f1(n)
s = 0
for i in 2:n
s += sum(( ((j^2-1)/(j-1) ) for j in 2:i)
end
return s
end
```

f1(5) gives 105

```
function f2(n)
s = 0
for i in 2:n
s += sum( j+1 ) for j in 2:i)
end
return s
end
```

f2(5) gives 40.

(j^2-1)/(j-1) should be the same than (j+1)

What am I doing wrong?