If the general term formula of the sequence {an} is an = n / (n ^ 2 + 156) (n ∈ n +), find the term with the largest mean value of the sequence

If the general term formula of the sequence {an} is an = n / (n ^ 2 + 156) (n ∈ n +), find the term with the largest mean value of the sequence

Please use the idea of mean inequality to solve the problem! Divide the numerator and denominator by N at the same time, you will find