reserve X for set;
reserve a,b,c,k,m,n for Nat;
reserve i,j for Integer;
reserve r,s for Real;
reserve p,p1,p2,p3 for Prime;

theorem Th57:
  22|^2 - 1 = 3*7*23
  proof
    22|^2 = 22*22 by WSIERP_1:1;
    hence thesis;
  end;
