Chapter 11 - Review - Page 667: 19

$a_n=\dfrac{3}{10}\left(\dfrac{1}{10} \right)^n$

The sequence $ \dfrac{3}{10},\dfrac{3}{100},\dfrac{3}{1000},... $ forms a geometric sequence. Hence, the general term of the sequence is \begin{array}{l} a_n=\dfrac{3}{10}\left(\dfrac{1}{10} \right)^n .\end{array}