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# Paul Leyland

He has contributed to the factorization of RSA-129, RSA-140 and RSA-155, as well as potential factorial primes as large as 400! + 1. He has also studied Cunningham numbers, Cullen numbers, Woodall numbers, etc., and numbers of the form $\displaystyle{ x^y + y^x }$, which are now called Leyland numbers.