John B. Cosgrave


Dr. John B. Cosgrave is an Irish mathematician specialising in number theory. Educated at Royal Holloway College, London, he lectured in Carysfort College and St Patrick's College of Education.

Other

In January 1999, while preparing some work for his students, he identified a highly structured prime number with exactly two thousand digits. Dubbing this prime a millennium prime, he wrote an email about it to a niece and nephew, which was subsequently published by Folding Landscapes, the publishing house of the cartographer Tim Robinson. He donated his author royalties to the Irish Cancer Society, and subsequently wrote an Irishman's Diary column about it for the Irish Times newspaper.
In July 1999 – while a participant in the Proth Search Group – he became the discoverer of the then-largest known composite Fermat number, a record which his St. Patrick's College based Proth-Gallot Group twice broke in 2003, the 1999 record having stood until then. The third of those records continued to stand until it was broken in June 2011.

Selected publications