\begin{table}%t2
\caption{\label{tbl:combinations}Parents ($p_1,p_2$) and their orders~($n_1,n_2$) of combination \protect frequencies~$f_{\rm c}$.}
\par
%\centering
\small 
\begin{tabular}{lrrrrrl}
\hline\hline
&&&&&& \\[-8pt]
ID & $n_1$ & $f_1$ (d$^{-1}$) & $n_2$ & $f_2$ (d$^{-1}$) & $f_{\rm c}$ (d$^{-1}$) & 
$\Delta$ (d$^{-1}$)\\
\hline
$d_{1,3}(1,1)$  & 1 & 5.48689 & 1  & 6.32482 &  11.81164 & 0.00006\\
$d_{1,3}(-1,1)$ &--1 & 5.48689 & 1  & 6.32482 &   0.83794 & 0.00001\\
$d_{1,3}(2,1)$  & 2 & 5.48689 & 1  & 6.32482 &  17.29841 & 0.0002 \\
$d_{1,3}(2,-1)$ & 2 & 5.48689 & --1 & 6.32482 &   4.64845 & 0.0005 \\
$d_{1,2}(1,1)$ & 1 & 5.48689 &  1 & 0.29917 &   5.78662 & 0.0006 \\
$d_{1,2}(1,-1)$ & 1 & 5.48689 & --1 & 0.29917 &   5.18781 & 0.00009 \\
$d_{1,2}(2,-1)$ & 2 & 5.48689 & --1 & 0.29917 &  10.67458 & 0.00002 \\
$d_{1,2}(2,-2)$ & 2 & 5.48689 & --2 & 0.29917 &  10.37493 & 0.0005 \\
$d_{1,2}(1,-3)$ & 1 & 5.48689 & --3 & 0.29917 &   4.58920 & 0.0002 \\
$d_{1,4}(1,1)$  & 1 & 5.48689 &  1 & 8.40918 &  13.89585 & 0.0002 \\
$d_{1,4}(-1,1)$  &--1 & 5.48689 &  1 & 8.40918 &   2.92159 & 0.0007 \\
$d_{1,6}(1,1)$  & 1 & 5.48689 &  1 & 6.14336 &  11.63039 & 0.0001 \\
$d_{1,8}(1,1)$  & 1 & 5.48689 &  1 & 7.35867 &  12.84432 & 0.001 \\
$d_{1,10}(1,1)$ & 1 & 5.48689 &  1 & 8.77086 &  14.25740 & 0.0003 \\
$d_{1,11}(1,1)$ & 1 & 5.48689 &  1 & 6.26517 &  11.75173 & 0.0003 \\
$d_{5,6}(1,-1)$ & 1 & 7.25476 & --1 & 6.14336 & 1.11216 & 0.0008 \\
$d_{5,6}(2,-1)$ & 2 & 7.25476 & --1 & 6.14336 & 8.36870 & 0.0025 \\
$d_{4,8}(1,-1)$ & 1 & 8.40918 & --1 & 7.35866 & 1.04985 & 0.0007 \\
$d_{7,9}(1,3)$ & 1 & 7.10353 &  3 & 0.89870 & 9.79999 & 0.0003 \\[2pt]
\hline
\end{tabular}
\end{table}