Erdős–Tenenbaum–Ford constant

The Erdős–Tenenbaum–Ford constant is a mathematical constant that appears in number theory. Named after mathematicians Paul Erdős, Gérald Tenenbaum, and Kevin Ford, it is defined as

${\displaystyle \delta$ :=1-{\frac {1+\log \log 2}{\log 2}}=0.0860713320\dots }

where ${\displaystyle \log }$ is the natural logarithm.

Following up on earlier work by Tenenbaum, Ford used this constant in analyzing the number ${\displaystyle H(x,y,z)}$ of integers that are at most ${\displaystyle x}$ and that have a divisor in the range ${\displaystyle [y,z]}$.