We use cookies to ensure you have the best browsing experience on our website. Please read our cookie policy for more information about how we use cookies.
  • Practice
  • Certification
  • Compete
  • Career Fair
  • Hiring developers?
  1. All Contests
  2. ProjectEuler+
  3. Project Euler #245: Coresilience

Project Euler #245: Coresilience

Problem
Submissions
Leaderboard
Discussions

This problem is a programming version of Problem 245 from projecteuler.net

We shall call a fraction that cannot be cancelled down a resilient fraction.

Furthermore we shall define the resilience of a denominator, , to be the ratio of its proper fractions that are resilient; for example, consider . The proper fractions with a denominator are . Four of these cannot be cancelled down, so the resilience is .

The resilience of a number is then

where φ is Euler's totient function.

We further define the coresilience of a number as

Given an integer , find the sum of all integers for which is a unit fraction, that is, a fraction with a numerator of after cancelling down.

Input Format

Each test file contains a single line containing a single integer .

Constraints

Output Format

Print the integer value of the sum of all integers for which is a unit fraction.

Sample Input 0

5

Sample Output 0

10

Explanation 0

Integer 2 3 4 5
Euler Phi 1 2 2 4
Coresilience 1/1 1/2 2/3 1/4



The sum of integers with Coresilience a unit fraction:   .

Author

kmcshane

Difficulty

Hard

Max Score

100

Submitted By

787

Need Help?


View discussions
View top submissions

rate this challenge

MORE DETAILS

Download problem statement
Download sample test cases
Suggest Edits
  • Contest Calendar
  • Blog
  • Scoring
  • Environment
  • FAQ
  • About Us
  • Support
  • Careers
  • Terms Of Service
  • Privacy Policy
  • Request a Feature