theorem
  141 satisfies_Sierpinski_problem_89
  proof
    set n = 141;
    thus n is_a_product_of_two_different_primes
    proof
      take P3,P47;
      thus thesis;
    end;
    thus n+1 is_a_product_of_two_different_primes
    proof
      take P2,P71;
      thus thesis;
    end;
    thus n+2 is_a_product_of_two_different_primes
    proof
      take P11,P13;
      thus thesis;
    end;
  end;
