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The factorization of the ninth Fermat number

Authors: A. K. Lenstra, H. W. Lenstra, M. S. Manasse and J. M. Pollard
Journal: Math. Comp. 61 (1993), 319-349
MSC: Primary 11Y05; Secondary 11Y40
Addendum: Math. Comp. 64 (1995), 1357.
MathSciNet review: 1182953
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Abstract: In this paper we exhibit the full prime factorization of the ninth Fermat number $ {F_9} = {2^{512}} + 1$. It is the product of three prime factors that have 7, 49, and 99 decimal digits. We found the two largest prime factors by means of the number field sieve, which is a factoring algorithm that depends on arithmetic in an algebraic number field. In the present case, the number field used was $ {\mathbf{Q}}(\sqrt[5]{2})$. The calculations were done on approximately 700 workstations scattered around the world, and in one of the final stages a supercomputer was used. The entire factorization took four months.

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Keywords: Fermat number, factoring algorithm
Article copyright: © Copyright 1993 American Mathematical Society

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