theorem Th5:
  for D being non empty set, f being FinSequence of D st
    f just_once_values f/.len f holds f:-f/.len f = <*f/.len f*>
proof
  let D be non empty set, f be FinSequence of D;
  assume
A1: f just_once_values f/.len f;
  thus f:-f/.len f = <*f/.len f*>^(f/^f/.len f..f) by FINSEQ_5:def 2
    .= <*f/.len f*>^(f/^len f) by A1,Th1
    .= <*f/.len f*>^{} by RFINSEQ:27
    .= <*f/.len f*> by FINSEQ_1:34;
end;
