reserve n for Nat,
  k for Integer;

theorem Th16:
  for x being object, p,q being FinSequence holds
  (p ^ q ^ <*x*>).((len p) + (len q) + 1) = x
proof
  let x be object, p,q be FinSequence;
  set s = p ^ q;
  (s ^ <*x*>).((len s) + 1) = x by FINSEQ_1:42;
  hence thesis by FINSEQ_1:22;
end;
