theorem Th30:
  for n being non zero Nat holds
  support Euler_factorization_2 n = dom Euler_factorization_2 n
  proof
    let n be non zero Nat;
    set f = Euler_factorization_2 n;
    thus support f c= dom f by PRE_POLY:37;
    let p be object;
    assume
A1: p in dom f;
    then reconsider p as Prime by Th29;
    f.p = p-1 by A1,Def3;
    hence thesis by PRE_POLY:def 7;
  end;
