He chaired the Norwegian Students' Society, edited Norsk matematisk Tidsskrift, and lectured at the University of Oslo.

Lange-Nielsen was born in Eivindvik in Gulen; the son of physician Johan Fredrik Nielsen and Christine Lange.

[1] Lange-Nielsen finished his secondary education in 1908, and attended the Norwegian Military Academy in 1909.

He graduated candidatus realium in 1917, and subsequently studied mathematics in Lund and in Paris.

[5] While at Grini, he took part in what has been described as the first actual political discussions in the camp, along with Erling Bühring-Dehli, Olaf Solumsmoen and others.