\[\boxed{\text{607\ (}\text{с}\text{).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[S_{n} = \frac{\left( a_{1} + a_{n} \right)}{2} \cdot n,\]
\[a_{n} = 3n + 2;\ \ a_{1} = 3 + 2 = 5:\ \]
\[a_{20} = 60 + 2 = 62\ \ \]
\[S_{20} = \frac{5 + 62}{2} \cdot 20 = 670.\]