Wilhelm Ljunggren

Wilhelm Ljunggren (7 October 1905 – 25 January 1973) was a Norwegian mathematician, specializing in number theory.

He studied at the University of Oslo, earning a master's degree in 1931 under the supervision of Thoralf Skolem, and found employment as a secondary school mathematics teacher in Bergen, following Skolem who had moved in 1930 to the Chr.

In 1943 he became a fellow of the Norwegian Academy of Science and Letters, and he also joined the Selskapet til Vitenskapenes Fremme.

[1][2][3] Ljunggren's research concerned number theory, and in particular Diophantine equations.

[5][6][7] Ljunggren also posed the question of finding the integer solutions to the Ramanujan–Nagell equation (or equivalently, of finding triangular Mersenne numbers) in 1943,[8] independently of Srinivasa Ramanujan who had asked the same question in 1913.