reserve X for set;
reserve a,b,c,k,m,n for Nat;
reserve i,j for Integer;
reserve r for Real;
reserve p,p1,p2 for Prime;

theorem Th48:
  17|^2 + 1 = 2*5*29
  proof
    17|^2 = 17*17 by WSIERP_1:1;
    hence thesis;
  end;
