73 -> 2n+1 ever prime?
Warut Roonguthai
warut at ksc9.th.com
Sun Jan 2 23:09:29 CET 2000
Chris Nash kindly reminded me that:
The xth iteration of the process n -> 2n+1 is (n+1)*2^x-1. Rigorous
primality proving of numbers of this form is easy and can be done with
Yves Gallot's Proth or PrimeForm. Or, you can use the tables at
http://vamri.xray.ufl.edu/proths/riesel2.html and
http://vamri.xray.ufl.edu/proths/rieselprob.html
Note that the sequence we are discussing is finite because of the
existence of a Riesel number, an odd number k such that k*2^x-1 is
composite for all positive integers x.
Happy New Year 2000!
Best wishes,
Warut
More information about the SeqFan
mailing list