\begin{figure}[H]
  \begin{center}
    \unitlength=4pt
    \begin{picture}(80, 14)(0,0)
    \gasset{Nw=1,Nh=1,Nmr=0.5,Nframe=n,curvedepth=0}
    \thinlines
    \node(A0)(0,0){$\bullet$}
    \node(Aa)(10,7){$\bullet$}
    \node(Aaa)(20,14){$\bullet$}
    \node(Aab)(20,0){$\bullet$}
    \node(Aaba)(30,7){$\bullet$}
    \node(Aabaa)(40,14){$\bullet$}
    \node(Aabab)(40,0){$\bullet$}
    \node(Aababa)(50,7){$\bullet$}
    \node(Aababaa)(60,14){$\bullet$}
    \node(Aababab)(60,0){$\bullet$}
    \node(Aabababa)(70,7){$\bullet$}
    \node(Aabababaa)(80,14){$\bullet$}
    \node(Aabababab)(80,0){$\bullet$}
    \put(78,6.2){$\cdots$}
    \drawedge[AHnb=0,ELside=l](A0,Aa){}
    \drawedge[AHnb=0,ELside=l](Aa,Aaa){}
    \drawedge[AHnb=0,ELside=l](Aa,Aab){}
    \drawedge[AHnb=0,ELside=l](Aab,Aaba){}
    \drawedge[AHnb=0,ELside=l](Aaba,Aabaa){}
    \drawedge[AHnb=0,ELside=l](Aaba,Aabab){}
    \drawedge[AHnb=0,ELside=l](Aabab,Aababa){}
    \drawedge[AHnb=0,ELside=l](Aababa,Aababaa){}
    \drawedge[AHnb=0,ELside=l](Aababa,Aababab){}
    \drawedge[AHnb=0,ELside=l](Aababab,Aabababa){}
    \drawedge[AHnb=0,ELside=l](Aabababa,Aabababaa){}
    \drawedge[AHnb=0,ELside=l](Aabababa,Aabababab){}
    \end{picture}
  \end{center}
  \caption{L'arbre associé au code préfixe $a(ba)^*a$.}
\end{figure}