reserve U for Universe;
reserve x for Element of U;

theorem
  for X being set for n being non zero Nat st
  n-tuples_on {X} is Element of U holds X is Element of U
  proof
    let X be set;
    let n be non zero Nat;
    assume n-tuples_on {X} is Element of U;
    then Funcs(Seg n ,{X}) is Element of U by FINSEQ_2:93;
    hence thesis by Th19;
  end;
