Hi can someone please help me and explain this problem to me?

We have

6

∑   5  + 6n

n = 1

When

n = 1   we have  11

n = 2  we have 17  

And we are summing these through n   = 6   ( = 41  )

Note :  This  is not unique.....there are  other ways, as  well, depending upon our starting value for n

Another possibility is

5

∑  11 + 6n

n = 0

Hope that helps !!!!