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

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,

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