In reply to emin:
In this case, there is no difference because the sequence is one term. However, let the sequence to be repeated is longer than one term.
|-> ##1 (b ##2 c)[*2]); // same as
##1 (b ##2 c) ##1 (b ##2 c)
|-> (##1 b ##2 c)[*2]); // same as
(##1 b ##2 c) ##1 (##1 b ##2 c)
// The difference :
##1 (b ##2 c) ##1 (b ##2 c) // |-> ##1 (b ##2 c)[*2]);
(##1 b ##2 c) ##1 (##1 b ##2 c) // |-> (##1 b ##2 c)[*2]);
// ^^^