Lehmer n→∞ nnames a problem asking whether there exists an n such that this function of n divides n − 1; no such numbers are known.
This function satis es the equation lim inf THIS(n) ln ln n = e−γ . Lehmer n→∞ nnames a problem asking whether there exists an n such that this function of n divides n − 1; no such numbers are known. A theorem named for this function states that for all a relatively prime to n, aTHIS(n) is congruent to   1 mod n. For prime numbers p, this function of p is equal to p−1. For ten points, identify this function which gives the number of integers less than a certain integer which are relatively prime to it and is symbolized by a phi.
This function satis es the equation lim inf THIS(n) ln ln n = e−γ .
Euler's totient function [prompt on Euler's phi function until read]