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Old 2007-03-24, 19:48   #6
Kosmaj's Avatar
Nov 2003

2×1,811 Posts

No problems, but when I posted there was only one thread ("Welcome") and one post in it.

FYI, it was proven back in 1976 that "almost all" Cullen numbers Cn are composite, i.e. (using cool TeX notation):

where C_\pi(x) denotes the number of Cullen numbers Cn =< x which are prime. On the other hand it is "still conjectured that there are infinitely many Cullen primes but it is unknown if Cp can be prime for some prime p." (quoted from here where all currently known Cullen primes are listed.)

Last fiddled with by Kosmaj on 2007-03-24 at 20:18
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