
theorem Th18:
  for D being non empty set, f,g being FinSequence of D
  st g is_odd_substring_of f,0 holds g is_odd_substring_of f,1
proof
  let D be non empty set, f,g be FinSequence of D;
  reconsider n = 0 as even Element of NAT;
  assume g is_odd_substring_of f,0;
  then g is_odd_substring_of f,n+1 by Th16;
  hence thesis;
