sentences:  Between January and August 1999, RSA-155, a challenge number prepared by the RSA company, was factorised using GNFS with relations again contributed by a large group, and the final stages of the calculation performed in just over nine days on the Cray C916 supercomputer at the SARA Amsterdam Academic Computer Center.In January 2002, Franke et al.announced the factorisation of a 158-digit cofactor of 2953+1, using a couple of months on about 25 PCs at the University of Bonn, with the final stages done using a cluster of six Pentium-III PCs.