A019294(461)

[Ralf Stephan]

Hugo:
> It takes less than 1 s of CPU time to factor 2^263-1 on an old 800 MHz
> Athlon using Dario Alpern's Java applet "Factorization using the
> Elliptic Curve Method" at http://www.alpertron.com.ar/ECM.HTM , even if
> the option "Use Cunningham tables on server" is not used.

But Alpern surely uses special algorithms for numbers of form
2^n-1 like the software of the GIMPS project. Pari does not have
these but I bet it's faster in the general case, as is ecm-6.


ralf