Image of Joseph Bertrand

Joseph Bertrand

was born 200 years ago

11 March 1822

Joseph Bertrand was a Paris professor who, in 1845, conjectured:

          I've told you once and I'll tell you again
          There's always a prime between n and 2n.


This was proved by Chebyshev in 1850.

Find out more at: https://mathshistory.st-andrews.ac.uk/Biographies/Bertrand/