Rich words in the block reversal of a word.

The block reversal of a word w , denoted by B R (w) , is a generalization of the concept of the reversal of a word, obtained by concatenating the blocks of the word in the reverse order. We characterize non-binary and binary words whose block reversal contains only rich words. We prove that for a binary word w , richness of all elements of B R (w) depends on l (w) , the length of the run sequence of w. We show that if all elements of B R (w) are rich, then 2 ≤ l (w) ≤ 8. We also provide the structure of such words. [ABSTRACT FROM AUTHOR]