The story
Listed by Edmund Landau at the International Congress of Mathematicians in 1912.
Etymology from Wiktionary, CC BY-SA 4.0.
Landau's problems
Today it means: Four basic unsolved problems about prime numbers: (i) is Goldbach's conjecture true?; (ii) is the twin prime conjecture true?; (iii) is Legendre's conjecture true?; (iv) are there infinitely many primes p such that p − 1 is a perfect square? Full definition →