[seqfan] Number of binary privileged words, etc

Neil Sloane njasloane at gmail.com
Thu Dec 28 08:47:16 CET 2017

Dear Sequence Fans,
This paper:

Gabriele Fici, Open and Closed Words, in Giovanni Pighizzini, ed., The
Formal Language Theory Column, Bulletin of EATCS, 2017,

discusses open words (A297183), closed words (A226452), and
privileged words (A231208)

The author also mentions that

" a privileged word is always closed, but there exist closed words that are
not privileged, e.g. abab, ababab, ababbabab, etc."

What is the number of closed words of length n that are not privileged ?

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