% This picture represents the ordinal number line
% (C) Thiago Brevidelli
\begin{tikzpicture}
  % The line
  \draw[-latex] (0,0) -- (6.5,0) node[right]{$\mathbf{ON}$}; 

  % The numbers
  \foreach \x in {0, 1, 2}
  \draw[shift={(\x,0)}] (0pt,3pt) -- (0pt,-3pt) node[below]{$\x$};

  \foreach \offset in {0, 3}
  \foreach \x in {2.5,2.75,2.875,2.9375,2.96875,2.984375} 
  \draw[shift={(\offset+\x,0)}] (0pt,3pt) -- (0pt,-3pt);

  \foreach \offset in {1, 2}
  \draw[shift={(3+\offset,0)}] (0pt,3pt) -- (0pt,-3pt)
                               node[below]{$\omega + \offset$};

  \draw[shift={(3,0)}] (0pt,3pt) -- (0pt,-3pt) node[below]{$\omega$};

  \draw[shift={(6,0)}] (0, 3pt) -- (0,-3pt) 
                       node[below]{$\omega + \omega$};
\end{tikzpicture}