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John Selfridge, mathematician, computer pioneer and philanthropist, 83, of DeKalb, Ill., died on Halloween, Oct. 31, 2010, just a week after his mentally-challenged daughter Margaret flew out to celebrate her birthday in his hospital room. John Selfridge, a mathematician's mathematician and a bon vivant's bad-boy, has found his last prime number and sung his last Al Jolsen song.
Born in Ketchikan, Alaska, the youngest of six children, he earned degrees from the University of Washington and UCLA and taught at various universities and greatly (exponentially?) expanded the Northern Illinois University Math Department during his tenure as chair. He also served as executive editor of Math Reviews. His Number Theory Foundation supported mathematicians, particularly graduate students, to attend conferences and join the larger family of number theorists.
For the last 10 years, Selfridge lived at the Oak Crest retirement community in DeKalb, regularly leaving for karaoke, math conferences, and ocean cruises. Before falling ill in the year 2000, Selfridge was an "itinerant mathematician," (his tax-preparer's description), visiting family, colleagues and ex-girlfriends all over. Selfridge was a pioneer in utilizing computers. As a graduate student in the 1950s, he used the 13 commands of the early SWAC computer to find two of the then-largest-known prime numbers. In February of this year, another computer search found a very large factor – 54 digits long – which proved Selfridge's 1964 conjecture that a certain Fermat number was not a prime.
He was a news junkie and life-long Democrat, often battling the U.S. State Department for denying visas to his friend Paul Erdos and other world-class mathematicians just because they had passports from Eastern Block countries. He is survived by daughters, Margaret and Barbara, an ex-wife and step-daughter, all of California; a host of nephews and nieces – he was "the Unc" – and many devoted personal attendants. More information about Selfridge's life is available online, at Wikipedia, at his daughter Barbara's Facebook page, and through the American Mathematical Society.
Selfridge's body has been donated to medical science, and there will be a memorial at 4 p.m. Saturday, Nov. 13, at Anderson Funeral Home, 2011 S. Fourth St., DeKalb.
For information, visit or call 815-756-1022.
In lieu of flowers, donations of any size can be made, tax-deductible, to The Number Theory Foundation, Math Department, Dartmouth College, Hanover, NH 03755.

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Published in Daily Chronicle from Nov. 11 to Nov. 14, 2010.
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