\begin{frame}
  \frametitle{Sigma Notation}

  \begin{block}{}
    We can use the \emph{sigma notation} to write sums more compactly:
    \begin{talign}
      \sum_{i = 1}^n h(i) \quad=\quad h(1) + h(2) + \ldots + h(n)
    \end{talign}
  \end{block}
  \pause
  \medskip
  
  \begin{exampleblock}{}
    \begin{malign}
      \sum_{i=1}^n i = \mpause[1]{1+2+3 +\ldots+n =} \mpause{ \frac{n(n+1)}{2} } 
    \end{malign}
  \end{exampleblock}  
  \pause\pause\pause
  \medskip
  
  \begin{exampleblock}{}
    \begin{malign}
      \sum_{i=1}^n i^2 = \mpause[1]{1^2 + 2^2 + 3^2 + \ldots+n^2} \mpause{= \frac{n(n+1)(2n+1)}{6}}
    \end{malign}
  \end{exampleblock}  
\end{frame}