True. I was just thinking that why Sage won't use the law of
congruences to evaluate the expression. 84977118993*2^520+1 is not too
large number to fit into the memory. Therefore one can use laws of
congruences to evaluate mod(2^(2^517)+1,84977118993*2^520+1).

On Jan 27, 5:21 pm, Marshall Hampton <[email protected]> wrote:
> The _result_ can certainly be verified by Sage somehow.  But to
> directly manipulate the expansion of something like 2^(2^517)+1 would
> be impossible, so care is needed in how to represent it.  In base 10,
> for example, that number has about 10^155 digits.  Given that there
> are roughly 10^52 electrons in the earth, it would be hard to deal
> with that.
>
> -M. Hampton
>
> On Jan 27, 5:14 am, Jaakko Seppälä <[email protected]> wrote:
>
> > I found onhttp://www.prothsearch.net/fermat.htmlthat84977118993*2^
> > {520} + 1 | 2^{2^517}+1. Can this result be verified by Sage?
>
> > sage: mod(2^(2^517)+1,84977118993*2^520+1)
> > ---------------------------------------------------------------------------
> > RuntimeError                              Traceback (most recent call
> > last)
>
> > /home/jaakko/Matikka/sage-4.2.1-linux-Ubuntu_9.10-i686-Linux/<ipython
> > console> in <module>()
>
> > /home/jaakko/Matikka/sage-4.2.1-linux-Ubuntu_9.10-i686-Linux/local/lib/
> > python2.6/site-packages/sage/rings/integer.so in
> > sage.rings.integer.Integer.__pow__ (sage/rings/integer.c:12061)()
>
> > RuntimeError: exponent must be at most 2147483647

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