
theorem
  283 is prime
proof
  now
    283 = 2*141 + 1; hence not 2 divides 283 by NAT_4:9;
    283 = 3*94 + 1; hence not 3 divides 283 by NAT_4:9;
    283 = 5*56 + 3; hence not 5 divides 283 by NAT_4:9;
    283 = 7*40 + 3; hence not 7 divides 283 by NAT_4:9;
    283 = 11*25 + 8; hence not 11 divides 283 by NAT_4:9;
    283 = 13*21 + 10; hence not 13 divides 283 by NAT_4:9;
  end;
  then for n being Element of NAT st 1 < n & n*n <= 283 & n is prime
  holds not n divides 283 by XPRIMET1:12;
  hence thesis by NAT_4:14;
end;
