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A375994
Number of distinct subsets of length-n words that can be the set of all length-n blocks occurring in some binary word.
1
4, 15, 122, 5922
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
Cf. A324149.
Sequence in context: A197703 A352608 A136506 * A362499 A323564 A246791
KEYWORD
nonn,more
AUTHOR
Jeffrey Shallit, Sep 05 2024
STATUS
approved