theorem Th59:
  17 divides 3|^1105-3
  proof
    3|^16|^69,1|^69 are_congruent_mod 17 by Lm1133,Lm1108,Lm1146,GR_CY_3:34;
    then 3|^1104*3,1*3 are_congruent_mod 17 by Lm1140,INT_4:11;
    then 3|^(1104+1),3 are_congruent_mod 17 by NEWTON:6;
    hence thesis;
  end;
