Thread: Primes of the form n+-phi(n) View Single Post
 2017-01-26, 01:02 #1 carpetpool     "Sam" Nov 2016 22·79 Posts Primes of the form n+-phi(n) Is there a way for finding all the primes < 1000 (or greater bound) which have the form n+-phi(n) (Just a reminder that phi is Euler's Phi Function.) The first such primes of these forms are 15-phi(15) = 7 and 15+phi(15) = 23. A list of numbers n such that n-phi(n) and or n+phi(n) are prime would also help here. Thanks.