\begin{figure}[H]
  \begin{center}
    \unitlength=4pt
    \begin{picture}(40, 56)(0,-28)
    \gasset{Nw=6,Nh=6,Nmr=3,curvedepth=3}
    \thinlines
    \node[Nmarks=if,iangle=0,fangle=0](A0)(0,0){$0$}
    \node(A1)(5.86,14.14){$1$}
    \node[Nmarks=f,fangle=270](A2)(20,20){$2$}
    \node(A3)(34.14,14.14){}          
    \node(A4)(34.14,-14.14){}
    \node[Nadjust=w](A5)(20,-20){$n-2$}
    \node[Nadjust=w](A6)(5.86,-14.14){$n-1$}
    \drawloop[loopangle=180](A0){$b$}
    \drawloop[loopangle=135](A1){$b$}
    \drawloop[loopangle=90](A2){$b$}
    \drawloop[loopangle=45](A3){$b$}
    \drawloop[loopangle=315](A4){$b$}
    \drawloop[loopangle=270](A5){$b$}
    \gasset{curvedepth=2}
    \drawedge(A0,A1){$a$}
    \drawedge(A1,A2){$a$}
    \drawedge(A2,A3){$a$}
    \drawedge(A4,A5){$a$}
    \drawedge(A5,A6){$a$}
    \drawedge(A6,A0){$a,b$}
    \put(35.89,10.14){$.$}
    \put(37.24,8.14){$.$}
    \put(38.27,6.14){$.$}
    \end{picture}
  \end{center}
  \caption{L'automate ${\cal A}_n$.}
\end{figure}