Easy Sequences 29: Odd proper divisors of odd proper divisors - MATLAB Cody - MATLAB Central

Problem 52804. Easy Sequences 29: Odd proper divisors of odd proper divisors

Difficulty:
(5)
Rate
The number is special. It has odd number of proper divisors: . Furthermore, if you take any of its proper divisors, say , it too has odd number of proper divisors: . The numbers and , have similar property as .
Given a limit n, find how many integers , have similar property as 210, namely, the integers should have odd number of proper divisors and all its proper divisors have odd number of proper divisors, as well.
The number , does not qualify because it has even proper divisors, 8 in total . The number also doesn't qualify because although it has proper divisors, some of its divisor, like , have even number of proper divisors.
NOTE: A proper divisor of a number, is a divisor which is less than the number. Exception to this rule is the number 1, which is considered a proper divisor of itself.
Solve

Solution Stats

66.67% Correct | 33.33% Incorrect
Last Solution submitted on May 26, 2023

Problem Comments

Solution Comments

Show comments

Problem Recent Solvers5

Suggested Problems

More from this Author116

Problem Tags

easy number theory simple

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!
Go to top of page