
%\bigskip
%\noindent\textbf{\large Summations}
\section{Summations}

\begin{displaymath}
  \sum_{k=1}^n k = \frac{n (n + 1)}{2} \ \ \ \ \ \ 
  \sum_{k=1}^n k^2 = \frac{n (n + 1) (2n + 1)}{6}
\end{displaymath}

{\footnotesize
\begin{displaymath}
  \sum_{k=1}^n k^3 = \frac{n^2 (n + 1)^2}{4} \ \ \ 
  \sum_{k=1}^n k^4 = \frac{n (n + 1) (2n + 1) (3n^2 + 3n - 1)}{30}
\end{displaymath}
}
%\normalsize

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