[Tex/LaTex] Help with the creation of this special table

Question

I will post down here the tableI need to create in LaTeX.

I actually have no clue with how to proceed. I only know basics tables codes.

Any help will be really appreciated!

P.s. I drew here a sample. I need actually more than three $\alpha$ cells and more than nine $t$ cells,but that won't be a problem of course: I will extend the code.

Thank you!!

About the size: I would like for the table to be quite large.

Not a landscape mode, but let's say $18$ cm in length. The height will depend upon how many $t$ and $\alpha$ I will put inside!

Answer 1

Taking partly into account an odd number of grouped rows, here a way, with multirow, array, caption and siunitx for the numbers alignment on the decimal dot in the last column.

\documentclass{article}

\usepackage[table]{xcolor}
\usepackage{multirow, array, caption}
\usepackage{siunitx}

\begin{document}

\begin{table}[!htb]
  \sisetup{table-format =1.11, table-number-alignment=center}
  \centering\setlength\extrarowheight{2pt}
  \caption{Title here}$ \begin{array}{|*{3}{c|}>{\color{red}}S|}%
  \hline
  \multirow{9}{*}{$ \sum_k f(k, \alpha, t) $}
  & & t = 0.1 & 0.123456789 \\
  \cline{3-4}  %
  &  \alpha= 1  & t = 0.5 & 1.04400440\\
  \cline{3-4}%
  &  & t = 0.9 & 2.71828182845 \\
  \cline{2-4}%
  & &t = 0.1 & 0.123456789\\ %
  \cline{3-4}%
  & \alpha=2  & t = 0.5 & 1.04400440\\
  \cline{3-4}%
  &  & t = 0.9 & 2.71828182845 \\
  \cline{2-4}%
  & &t = 0.1 &   \\
  \cline{3-4}%
  &  \alpha=3  & t = 0.5 &  \\
  \cline{3-4}%
  &  & t = 0.9 &  \\
  \hline%
  \end{array} $
\end{table}

\end{document}