2. List the natural numbers $1, 2, \cdots, k^{2}$ in a square table (as shown in Table 1), then select any one number from the table, and subsequently remove the row and column containing that number. Then, perform the same operation on the remaining $(k-1)^{2}$ numbers in the square table, and continue this process $k$ times. The sum of the $k$ selected numbers is
1
\begin{tabular}{|c|c|c|c|}
\hline 1 & 2 & $\cdots$ & $k$ \\
\hline$k+1$ & $k+2$ & $\cdots$ & $2 k$ \\
\hline$\cdots$ & $\cdots$ & $\cdots$ & $\cdots$ \\
\hline$(k-1) k+1$ & $(k-1) k+2$ & $\cdots$ & $k^{2}$ \\
\hline
\end{tabular}