theorem
  b,c are_coprime & b|^2 + c|^2 = a|^2 implies not 3 divides a
  proof
    b,c are_coprime & b|^2 + c|^2 = a|^2 implies
      not 3 divides a|^(1+1) by Th95;
    hence thesis by Th96,PEPIN:41;
  end;
