# Use geometric sequence formulas

Given the formula of a geometric sequence, either in explicit form or in recursive form, find a specific term in the sequence.

### Problem

The geometric sequence a, left parenthesis, n, right parenthesis is defined by the following formula:
a, left parenthesis, n, right parenthesis, equals, 1, left parenthesis, minus, 2, right parenthesis, start superscript, n, minus, 1, end superscript
What is the fourth term in the sequence?