Alford, Granville and Pomerance showed that there are an infinite number of these entities in a paper dedicated to Paul Erdos on his 80th birthday, and they also showed that there are approximately n to the power of two-sevenths of them between 1 and n.
Alford, Granville and Pomerance showed that there are an infinite number of these entities in a paper dedicated to Paul Erdos on his 80th birthday, and they also showed that there are approximately n to the power of two-sevenths of them between 1 and n. They are a subclass of Knodel numbers with n equals 1. If an integer n is square-free, and if all its prime divisors p have the property that p minus 1 divides n minus 1, n is necessarily one of these numbers; that test is known as Korselt's criterion. 561 is the first of these numbers, which manage to pass the Fermat primality test without being prime. For 10 points name these numbers n satisfying the congruence b to the n minus 1 similar to 1 (mod n) for all integers b which are relatively prime to n, named for an American mathematician.
Alford, Granville and Pomerance showed that there are an infinite number of these entities in a paper dedicated to Paul Erdos on his 80th birthday, and they also showed that there are approximately n to the power of two-sevenths of them between 1 and n.
Carmichael numbers (prompt on pseudoprime or Fermat pseudoprime, but accept absolute Fermat pseudoprime)