There are more than 2n/17 n-letter ternary square-free words.
Ekhad, Shalosh B. ; Zeilberger, Doron
Journal of Integer Sequences [electronic only], Tome 1 (1998), / Harvested from The Electronic Library of Mathematics
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Publié le : 1998-01-01
EUDML-ID : urn:eudml:doc:223525 
@article{01264511,
     title = {There are more than },
     journal = {Journal of Integer Sequences [electronic only]},
     volume = {1},
     year = {1998},
     zbl = {1018.68060},
     language = {en},
     url = {http://dml.mathdoc.fr/item/01264511}
}

Ekhad, Shalosh B.; Zeilberger, Doron. There are more than . Journal of Integer Sequences [electronic only], Tome 1 (1998) . http://gdmltest.u-ga.fr/item/01264511/