P69
projecteuler.net

Totient Maximum

ℹ️Published on Friday, 7th May 2004, 06:00 pm; Solved by 38686;
Difficulty rating: 10%

Euler's totient function, ϕ(n) [sometimes called the phi function], is defined as the number of positive integers not exceeding n which are relatively prime to n. For example, as 1, 2, 4, 5, 7, and 8, are all less than or equal to nine and relatively prime to nine, ϕ(9)=6.

n Relatively Prime ϕ(n) n/ϕ(n)
2 1 1 2
3 1,2 2 1.5
4 1,3 2 2
5 1,2,3,4 4 1.25
6 1,5 2 3
7 1,2,3,4,5,6 6 1.1666...
8 1,3,5,7 4 2
9 1,2,4,5,7,8 6 1.5
10 1,3,7,9 4 2.5

It can be seen that n=6 produces a maximum n/ϕ(n) for n10.

Find the value of n1000000 for which n/ϕ(n) is a maximum.



Soluzione

Last modified: June 14, 2025. Website built with Franklin.jl and the lovely Julia programming language.