reserve a,b,c for set;

theorem
  for f being FinSequence st f=<*a*> holds f|1=<*a*>
proof
  let f be FinSequence;
  assume
A1: f=<*a*>;
  then len f <=1 by FINSEQ_1:40;
  hence thesis by A1,FINSEQ_1:58;
end;
