mathematics The number of prime numbers less than x is

about x/log(x). Here "is about" means that the ratio of the

two things tends to 1 as x tends to infinity. This was first

conjectured by Gauss in the early 19th century, and was

proved (independently) by Hadamard and de la Vall'ee Poussin

in 1896. Their proofs relied on complex analysis, but Erdos

and Selberg later found an "elementary" proof.