\centerline{
 \beginpicture
 \setcoordinatesystem units <1.0cm,1.0cm>
 \setlinear
 \setdots % speed up PiCTeX
%
 \put {$A$} [b] <0mm,1.5mm>  at 3.0 2.5
 \put {$\bullet$} at 3.0 2.5
%
 \put {$v_1$} [t] <0mm,-1.5mm> at 0.0 0.0
 \put {$\bullet$} at 0.0 0.0
 \plot 0.0 0.0  3.0 2.5 /
%
 \put {$v_2$} [t] <0mm,-1.5mm> at 1.0 0.0
 \put {$\bullet$} at 1.0 0.0
 \plot 1.0 0.0  3.0 2.5 /
%
 \put {$\bullet$} at 2.5 0.0
 \plot 2.5 0.0  3.0 2.5 /
%
 \put {$\bullet$} at 3.5 0.0
 \plot 3.5 0.0  3.0 2.5 /
%
 \put {$\bullet$} at 4.5 0.0
 \plot 4.5 0.0  3.0 2.5 /
%
 \put {$v_n$} [t] <0mm,-1.5mm> at 6.0 0.0
 \put {$\bullet$} at 6.0 0.0
 \plot 6.0 0.0  3.0 2.5 /
%
 \endpicture
}