OFFSET
1,1
COMMENTS
Another way to say this is that a(n) is the number of distinct sets of vertices of the de Bruijn graph of order n encountered by some walk on the graph.
EXAMPLE
For n = 2, the only set not counted is {00,11}, since if a word has 00 and 11 as blocks appearing in it, then it must have either 01 or 10 also.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Jeffrey Shallit, Sep 05 2024
STATUS
approved