TeX source:

\begin{array}{ll}n=1 & a_{1}=9 \\n=2 & a_{2}=3 a_{1}-20=3(9)-20=27-20=7 \\n=3 & a_{3}=3 a_{2}-20=3(7)-20=21-20=1 \\n=4 & a_{4}=3 a_{3}-20=3(1)-20=3-20=-17 \\n=5 & a_{5}=3 a_{4}-20=3(-17)-20=-51-20=-71\end{array}