\begin{table}%t2
\caption{\label{tab:2}Values of the parameters~\textit{a, b,} and $\sigma^{2}$ assumed for the function $f\left(r\right)=\cos^{a}\left(b\pi r\right)\exp\left(-\frac{r^{2}}{2\sigma^{2}}\right)$
and the number of generations needed to reach an error tolerance of~$10^{-6}$. }
\par
%%\centering

\small
\begin{tabular}{cccc}
\hline \hline
&&& \\[-8pt]
\textit{a}&
\textit{b}&
$\sigma^{2}$&
Ngen\\
\hline
2&
3&
1&
65\\
2&
3&
2&
69\\
2&
3&
4&
66\\
2&
9&
1&
94\\
2&
9&
2&
94\\
2&
9&
4&
91\\
4&
3&
1&
69\\
4&
3&
2&
66\\
4&
3&
4&
58\\
4&
9&
1&
94\\
4&
9&
2&
101\\
4&
9&
4&
98\\
\hline
\end{tabular}
\end{table}