Paul Gage and I found it while testing system software on a C90 at the Cray Research central computing facility. The Lucas-Lehmer test ran in 25,924 cpu seconds. I still do the "old" non-elastic transform multiply.
Richard Crandall has independently verified this exponent.
slow -- Bob Silverman These are my opinions and not MITRE's. Mitre Corporation, Bedford, MA 01730 "You can lead a horse's ass to knowledge, but you can't make him think"