Thanks to Hans Lundmark, I just found the table of Clifford algebras $C_k=C_{\Bbb R}(0,k)$ and $C'_k=C_{\Bbb R}(k,0)$, $0\leq k\leq 7$. But, I couldn't understand some of the slots in the table.
$\begin{array}{|c|c|c|} \hline\\ k&C_k&C'_k\\\hline 0&\Bbb R&\Bbb R\\\hline 1&\Bbb C&\Bbb R\oplus\Bbb R\\\hline 2&\Bbb H&\color{red}{\Bbb R(2)}\\\hline 3&\Bbb H\oplus\Bbb H&\\\hline 4&\Bbb H(2)&\\\hline 5&&\\\hline 6&&\\\hline 7&&\\\hline \end{array}$
My bad. I forgot them again although I looked at Wikipedia. Can somebody please help me to fill this table giving also some ideas to remember them?
Thank you for reading.