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.
Hansraj Gupta's Theorem 2 of his 1981 paper: the number vo of odd members of ϕ-1(2k) is 1 if 0 ≤ k < 32 and 0 for k ≥ 32. Furthermore, that paper includes an explicit list for m=576, as well as a useful table of even-odd checksums for ϕ-1([1,...,m]).
In Python testcases, the limit for time is 20 seconds and memory is 512 megabytes. My Python3 code runs under 360 milliseconds; its own prime factorization uses memo-ization.
Cookie support is required to access HackerRank
Seems like cookies are disabled on this browser, please enable them to open this website
Project Euler #248: Numbers for which Euler’s totient function equals 13!
You are viewing a single comment's thread. Return to all comments →
To check the cardinality ("checksum") of your sets ϕ-1(m), consider these resources I used:
In Python testcases, the limit for time is 20 seconds and memory is 512 megabytes. My Python3 code runs under 360 milliseconds; its own prime factorization uses memo-ization.