Sounds like homework, but I will give you some hints:
v = 1:n; % <-- make a vector with the numbers 1, 2, 3, ..., n
1 ./ whatever % <-- does the divide element-by-element
whatever .^ 2 % <-- does the squaring element-by-element
So you should be able to combine the above operations appropriately to get the approximation you are after. (Although, as a nit, this will not "prove" it).
