Ernst Jacobsthal

Ernst Erich Jacobsthal (1882 to 1965) was a German mathematician born in Berlin, younger brother of the archaeologist Paul Jacobsthal. He studied at the University of Berlin under Frobenius, Schwarz and Schur, and took his doctorate in 1906 with a thesis on a formula from the theory of quadratic residues that gives a proof that every prime of the form 4n plus 1 is a sum of two squares. He taught at a Berlin school and lectured at the Technical University of Berlin until 1934, when he was dismissed because of his Jewish origins. He emigrated to Norway in 1939 and later became a professor at the Norwegian Institute of Technology in Trondheim. His papers range across algebra, analysis, function theory and number theory, and the Jacobsthal numbers and Jacobsthal sums carry his name.