#
Axel Thue

Axel Thue was born in Tönsberg, Norway, on February 19, 1863.
In 1889 he received a degree at the
University of Oslo. From 1903 until 1922 he was professor
in applied mechanics at the University of Oslo. He was
elected to the Norweigian Academy of Science and Letters in 1894,
and he was associate editor of *Acta Mathematica* from
1916-1922.
Thue is sometimes known as the "father of formal languages". He was
the first to investigate the problem of finding an infinite sequence
over a finite alphabet that did not contain any occurrences of
adjacent identical blocks, a property today known as
*squarefreeness*. Unfortunately, because his papers on
repetitions in words were published in a
relatively obscure Scandinavian journal, his work was forgotten
and later rediscovered by many writers, such as Max Euwe and
Marston Morse. However, Gustav Hedlund later rediscovered
Thue's contribution and popularized it.

Thue also made fundamental contributions to number theory
(particularly transcendence theory).

Thue died in Oslo, Norway, on March 7, 1922.

## Sources

- J. Berstel, Axel Thue's papers on repetitions in words: a
translation, Publications du Laboratoire de Combinatoire et
d'Informatique Mathématique, Université du
Québec à Montréal, No. 20, 1995.
- G. Hedlund, Remarks on the work of Axel Thue on sequences,
*Nordisk Mat. Tidskrift* **15** (1967), 148-150.
- T. Nagell, A. Selberg, S. Selberg, and K. Thalberg, eds.,
*Selected Mathematical Papers of Axel Thue*, Universitetsforlaget,
Oslo, 1977.

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September 10 1997