reserve a,b,k,m,n,s for Nat;
reserve c,c1,c2,c3 for Complex;
reserve i,j,z for Integer;
reserve p for Prime;
reserve x for object;
reserve f,g for complex-valued FinSequence;

theorem Th54:
  len(f^2) = len f
  proof
    dom(f^2) = dom f by VALUED_1:11;
    hence thesis by FINSEQ_3:29;
  end;
