,n=1,2,3,..., here we see that when we increase the value of n like as 1,2,3,... the value of an increases but when we reach at n=9 or 10 the value of an remain unchanged, ie, minor difference in after decimal places and when we cross the value n=10 ie, n=11, then we see that the value of an is monotonically decreasing. Hence, an have its maximum value at n=9 or 10.