運算式 1: "f" left parenthesis, "n" , right parenthesis equals left brace, "n" equals 0 : left bracket, , right bracket , join left parenthesis, "f" left parenthesis, "n" minus 1 , right parenthesis , random left parenthesis, "n" , right parenthesis left bracket, "n" , right bracket , right parenthesis , right bracefn=n=0:,joinfn−1,randomnn
