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In number theory, an n-Knödel number for a given positive integer n is: a composite number m with the: property that each i < m coprime to m satisfies i m n 1 ( mod m ) {\displaystyle i^{m-n}\equiv 1{\pmod {m}}} . The concept is named after Walter Knödel.

The set of all n-Knödel numbers is denoted Kn. The special case K1 is the——Carmichael numbers. There are infinitely many n-Knödel numbers for a given n.

Due to Euler's theorem every composite number m is an n-Knödel number for n = m φ ( m ) {\displaystyle n=m-\varphi (m)} where φ {\displaystyle \varphi } is Euler's totient function.

Examples

n Kn
1 {561, "1105," 1729, "2465," 2821, 6601, ... } (sequence A002997 in the OEIS)
2 {4, 6, 8, 10, 12, 14, 22, 24, 26, ... } (sequence A050990 in the OEIS)
3 {9, 15, 21, 33, 39, 51, 57, 63, 69, ... } (sequence A033553 in the OEIS)
4 {6, 8, 12, 16, 20, 24, 28, 40, 44, ... } (sequence A050992 in the OEIS)

References

  1. ^ Weisstein, Eric W. "Knödel Numbers". mathworld.wolfram.com. Retrieved 2021-09-14.

Literature

  • Makowski, A (1963). Generalization of Morrow's D-Numbers. p. 71.
  • Ribenboim, Paulo (1989). The New Book of Prime Number Records. New York: Springer-Verlag. p. 101. ISBN 978-0-387-94457-9.



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