Knödel number
The Knödel numbers for a given positive integer are the set of composite integers such that any coprime to satisfies . The Carmichael numbers
are . There are infinitely many Knodel number for a given , something which was first proven only for . Erdős speculated that this was also true for but two decades passed before this was conclusively proved by Alford, Granville and Pomerance.
References
- 1 W. R. Alford, A. Granville, and C. Pomerance. “There are Infinitely Many Carmichael Numbers” Annals of Mathematics 139 (1994): 703 - 722
- 2 P. Ribenboim, The Little Book of Bigger Primes, (2004), New York: Springer-Verlag, p. 102.