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Largest Fermat number with known factorization

which was factored by Brent & Morain in 1988. was factored by A.K. Lenstra, H.W. Lenstra Jr., M.S. Manasse & J.M. Pollard in 1990. was factored by Richard Brent who found a 40-digit factor of on October 20, 1995. The cofactor is a 252 digit number, which is not so easy to factor. Luckily, this number was also prime.

Alex Lopez-Ortiz
Mon Feb 23 16:26:48 EST 1998