OFFSET
0,2
COMMENTS
By an "instance of the pattern x y y x^R" we mean a nonempty block, followed by a second nonempty block (of a possibly different length), followed by the second block again, and ending with the first block reversed. An example in English is the word "redder": (re)(d)(d)(er).
CROSSREFS
KEYWORD
nonn
AUTHOR
Jeffrey Shallit, Jun 08 2018
STATUS
approved