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
  Euler_factorization p = p .--> (p-1)
  proof
    Euler_factorization (p|^1) = p .--> (p|^1-p|^(1-1)) by Th19;
    hence thesis by NEWTON:4;
  end;
