[tex]\bf \begin{array}{|ll|ll} \cline{1-2} \stackrel{a_n}{term}\qquad &\stackrel{\left( \frac{1}{3} \right)a_{n-1}}{value}\\ \cline{1-2} a_1&486\\&\\ a_2&\left( \frac{1}{3} \right)a_{2-1}\\&\\ &\left( \frac{1}{3} \right)a_{1}\\&\\ &\left( \frac{1}{3} \right)486\\&\\ &162\\&\\ a_3&\left( \frac{1}{3} \right)a_{3-1}\\&\\ &\left( \frac{1}{3} \right)a_{2}\\&\\ &54\\&\\ a_4&\left( \frac{1}{3} \right)a_{3}\\&\\ &18 &\\ \cline{1-2} \end{array}[/tex]
