% Title: Demonstration sans parole : somme des N premiers entiers impairs
% Author: Jacques Duma
% Site: http://math.et.info.free.fr/TikZ/index.html

\documentclass{article}

\usepackage{tikz}

\begin{document}

\pagestyle{empty}

\section*{Somme des  premiers nombres entiers impairs}

\vfill

\begin{center}
\begin{tikzpicture} [scale=0.75]
	\foreach \x in {0,2,...,14}
		\foreach \y in {0,2,...,14}
			\fill[ball color=magenta] (\x,\y) circle (0.5);
	\foreach \x in {1,3,...,14}
		\draw[ultra thick,gray] (\x,-1)--(\x,\x)--(-1,\x);     
	\draw[ultra thick,gray] (15,-1) rectangle (-1,15);     
\end{tikzpicture}
\end{center}

{\Huge $$1+3+5+\dots+(2n-1)=n^2$$}

\vfill

\end{document}
