%!PS

% We want the 'n'th fibonacci number
/n 13 def

% Prepare output canvas:
/Helvetica findfont 20 scalefont setfont
100 100 moveto

%define the function recursively:
/fib { dup
       3 lt
         { pop 1 }
         { dup 1 sub fib exch 2 sub fib add }
       ifelse
    } def

    (Fib\() show n (....) cvs show (\)=) show n fib (.....) cvs show

showpage