This kind of problem is generally to find the derivative and judge whether the derivative is greater than zero;

The derivation of this problem is = (6/7) n+(n+2) * n * (6/7) (n-1) = (6/7) (n-1) * (n * n+2 * n+6.

Constant is greater than 0; Monotonically increasing, so there is no maximum term.

Another method is to find the limit:

Because an is a positive term and the limit is positive infinity, there will be no maximum term.