reserve a,x,y for object, A,B for set,
  l,m,n for Nat;
reserve X,Y for set, x for object,
  p,q for Function-yielding FinSequence,
  f,g,h for Function;
reserve m,n,k for Nat, R for Relation;
reserve i,j for Nat;
reserve F for Function,
  e,x,y,z for object;
reserve a,b,c for set;

theorem Th119:
  for n st n > 0 holds (a followed_by b).n = b
proof
  let n;
A1: n in NAT by ORDINAL1:def 12;
  assume n > 0;
  hence (a followed_by b).n = (NAT --> b).n by Th31
    .= b by A1,FUNCOP_1:7;
end;
