We can see this is a summation of multiples of 8 plus 1, which starts at 1.
This can be written in the following way:
[tex] \Sigma_{m=0}^{n}(8m+1) [/tex]
Lets verify the summation expression by doing the sequence for the first 4 elements (hence [tex]n=3[/tex], as it starts from 0):
[tex]\Sigma_{m=0}^{3}(8m+1)=[8(0)+1]+[8(1)+1]+[8(2)+1]+[8(3)+1]=[/tex]
[tex]1+9+17+25[/tex]
As you can see, the generalization is correct.
