/N 20 def
/k 7 def

1 setlinewidth

%% on genere un polygone regulier a N sommets
/les_points O 5.5 N 0 genpolyreg def

%% on relie le point d'indice i au point d'indice k+i (mod N)
/i 0 def
N {
   les_points i getp 
   les_points i k add N mod getp
   1 trait
   /i i 1 add store
} repeat

%%/str 20 string def
%%setTimesItalic
%%   (n) xmax xmin 2 mul 3 div add .5 sub ymin text
%%setTimes
%%   ( = ) show
%%   N str cvs show
%%setTimesItalic
%%   (k) xmax xmin 4 mul 3 div add .5 sub ymin text
%%setTimes
%%   ( = ) show
%%   k str cvs show