A rhyme about a prime

     Tomorrow, May 16, is the birthday of Pafnuty Chebyshev (1821-1894), who was one of the founders of Russian mathematics and the first to prove (in 1850) a conjecture (about positive integers) made in 1845 by French mathematician Joseph Bertrand (1822-1900) and sometimes referred to as Bertrand's postulate.  This rhyming couplet celebrates that conjecture:

               Chebyshev said, and I'll say it again:
               There's always a prime between n and 2n.

Thanks to Evelyn Lamb's AMS Page-A-Day Calendar for its May 10 alert to the info above.