Cunningham number
In mathematics, specifically in number theory, a Cunningham number is a certain kind of integer named after English mathematician A. J. C. Cunningham.
Definition
Cunningham numbers are a simple type of binomial number – they are of the form
- [math]\displaystyle{ b^n\pm1 }[/math]
where b and n are integers and b is not a perfect power. They are denoted C±(b, n).
Primality
Establishing whether or not a given Cunningham number is prime has been the main focus of research around this type of number.[1] Two particularly famous families of Cunningham numbers in this respect are the Fermat numbers, which are those of the form C+(2, 2m), and the Mersenne numbers, which are of the form C−(2, n).
Cunningham worked on gathering together all known data on which of these numbers were prime. In 1925 he published tables which summarised his findings with H. J. Woodall, and much computation has been done in the intervening time to fill these tables.[2]
See also
- Cunningham project
References
- ↑ J. Brillhart, D. H. Lehmer, J. Selfridge, B. Tuckerman, and S. S. Wagstaff Jr., Factorizations of bn±1, b=2, 3, 5, 6, 7, 10, 11, 12 Up to High Powers (n), 3rd ed. Providence, RI: Amer. Math. Soc., 1988.
- ↑ R. P. Brent and H. J. J. te Riele, Factorizations of an±1, 13≤a<100 Report NM-R9212, Centrum voor Wiskunde en Informatica. Amsterdam, 1992.
External links
- Cunningham Number at MathWorld
- The Cunningham Project, a collaborative effort to factor Cunningham numbers
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