You can see that each term is getting three times its initial term. Upon dividing the each term by its previous term, it can be seen clearly (9/3 = 3 and 27/9 = 3).

Or

We can say that the given sequence is a part of a geometric progression with first term as 1 and common ratio as 3.

Hence, the required term will be three times the number 81 i.e., the required number is 81*3 = 243.