I tried factoring the 6th Fermat number using the code below and
got F6 returned to me, suggesting that F6 is prime. Since one
factor of F6 is 274177, this seems to contradict Section 10.20
of the documentation, which states that "FactorsInt is
guaranteed to find all factors less than 10^6."

gap> FactorsInt( 2^(2^6) + 1);
[ 18446744073709551617 ]
gap> (2^(2^6) + 1) / 274177;
67280421310721
gap> quit;

I doubt that it makes any difference, but my hardware is a Turbo
Color NeXTstation running NeXTSTEP 2.1. My version of GAP is 3.1,
obtained as gapexe.next from SAMSON.

Edward Spitznagel
Department of Mathematics
Washington University
c31801st@wuvmd.wustl.edu