Erdős–Tenenbaum–Ford constant

The Erdős–Tenenbaum–Ford constant is a mathematical constant that appears in number theory.

[1] Named after mathematicians Paul Erdős, Gérald Tenenbaum, and Kevin Ford, it is defined as where

Following up on earlier work by Tenenbaum, Ford used this constant in analyzing the number

[2][3][4] For each positive integer

be the number of distinct integers in an

In 1960,[5] Erdős studied the asymptotic behavior of