Code#5

\documentclass{article}
\usepackage{booktabs}
\usepackage{multirow}

\usepackage{array}
\newcolumntype{O}[1]{>{\raggedright\arraybackslash}m{#1}}
\newcolumntype{P}[1]{>{\centering\arraybackslash}m{#1}}
\newcolumntype{Q}[1]{>{\raggedleft\arraybackslash}m{#1}}
\newcolumntype{S}{>{\centering\arraybackslash}m{2cm}}

\begin{document}

\begin{table}[h]
\centering
\caption{My caption}
\label{my-label}

\begin{tabular}{@{}lcScP{2cm}@{}}
\toprule
   & Column & Column                    & Column                   & Column \\ \midrule
Row & 1      & 2                         & 3                        & $k=a+b+c+d+e+f+g$      \\
Row & 5      & \multicolumn{2}{c}{\multirow{2}{*}{Because why not}} & 8      \\
Row & 9      & \multicolumn{2}{c}{}                                 & 12     \\
Row & 13     & $k=a+b+c+d+e$                        & 15                       & 16     \\ \bottomrule
\end{tabular}

\end{table}

\end{document}