Person: Ljunggren, Wilhelm
Wilhelm Ljunggren was a Norwegian mathematician who specialised in number theory.
Mathematical Profile (Excerpt):
 Wilhelm attended secondary school in Oslo, graduating in 1925.
 Ljunggren won the prize in his final year at secondary school.
 Ljunggren graduated in 1931 and Thoralf Skolem, who was a student of Axel Thue, had advised him during the research for his Master's thesis.
 Skolem moved to the Christian Michelsen's Institute in Bergen as a Research Associate in 1930 and so Ljunggren, who wished to keep in contact with Skolem, accepted a position as a secondary school teacher in Bergen.
 Ljunggren undertook research in number theory during the years he taught at the secondary school in Bergen and he submitted his doctoral thesis to the University of Oslo in 1937.
 Ljunggren followed Skolem to Oslo, for in 1938 he became a teacher at the Hegedehaugen School.
 The University of Bergen was founded in 1946 and, three years later, Ljunggren was appointed as professor of mathematics there.
 Although Ljunggren quickly built up a strong teaching department in Bergen he took the opportunity to return to Oslo in 1956 when he was offered the chair of mathematics there.
 By this time Skolem was retiring and Ljunggren took over the responsibilities of keeping Oslo as a leading institution for mathematics.
 Ljunggren taught parttime at the Technical Institute to help his friend build its reputation.
 Almost all of Ljunggren's research was on Diophantine equations.
 One of Ljunggren's main interests was Diophantine equations of degree 4.
 In the paper Ljunggren found bounds for the number of integer solutions for some special equations of this type.
 Here is one further example of the results obtained by Ljunggren.
 On the other hand, Ljunggren submitted also many problems, addressed to university students as well as highschool pupils.
Born 7 October 1905, Oslo, Norway. Died 25 January 1973, Oslo, Norway.
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Origin Norway
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References
Adapted from other CC BYSA 4.0 Sources:
 Oâ€™Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive