Cullen number

A Cullen number $C_m$ is a number of the form $2^{m}m+1$, where $m$ is an integer. Almost all Cullen numbers are composite, and they have $2m-1$ as a factor if that number is a prime of the form $8k-3$ (with $k$ a positive integer). The first few Cullen numbers are 1, 3, 9, 25, 65, 161, 385, 897, 2049, 4609 (listed in A002064 of Sloane’s OEIS). With the exception of 3, no Proth number is also a Cullen number.

Title	Cullen number
Canonical name	CullenNumber
Date of creation	2013-03-22 17:21:34
Last modified on	2013-03-22 17:21:34
Owner	PrimeFan (13766)
Last modified by	PrimeFan (13766)
Numerical id	5
Author	PrimeFan (13766)
Entry type	Definition
Classification	msc 11A51
Related topic	WoodallNumber