\[a_{1} = 6;\ \ \]
\[a_{n} = 6n;\]
\[6n \leq 145\]
\[n \leq \frac{145}{6} \leq 24\frac{1}{6}.\]
\[n = 24.\]
\[a_{24} = 6 \cdot 24 = 144.\]
\[S_{24} = \frac{a_{1} + a_{24}}{2} \cdot 24 =\]
\[= (6 + 144) \cdot 12 =\]
\[= 150 \cdot 12 = 1800.\]
\[Ответ:1800.\]