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A108573 Least positive k such that k * [RSA-640]^n - 1 is prime, where RSA-640 is the 193 decimal digit RSA challenge number. 4
390, 1334, 136, 2058, 2710, 2082, 748, 2388, 3588, 1902, 988, 9170, 5076, 28778, 2112, 1800, 3082, 1238, 12916 (list; graph; refs; listen; history; text; internal format)



Other terms are a(25)=1558 and a(43)=5718. All values in the sequence are Fermat and Lucas PRPs except for the first two which were proved with ECM. The larger values won't be easily provable until RSA-640 is factored, which has a prize of $20,000 for its factorization. This sequence is based on a suggestion of Jens Kruse Andersen.

RSA-640 was factored in 2005; see the Wikipedia link. - D. S. McNeil, Nov 26 2010


Table of n, a(n) for n=1..19.

Wikipedia, RSA-640


Cf. A108375.

Sequence in context: A136153 A069477 A325993 * A206653 A202429 A236612

Adjacent sequences:  A108570 A108571 A108572 * A108574 A108575 A108576




Jason Earls, Jul 05 2005


Edited and a(19) added by D. S. McNeil, Nov 25 2010



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Last modified December 3 05:05 EST 2021. Contains 349445 sequences. (Running on oeis4.)