A108573 - OEIS

A108573

Least positive k such that k * [RSA-640]^n - 1 is prime, where RSA-640 is the 193 decimal digit RSA challenge number.

390, 1334, 136, 2058, 2710, 2082, 748, 2388, 3588, 1902, 988, 9170, 5076, 28778, 2112, 1800, 3082, 1238, 12916

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OFFSET

1,1

COMMENTS

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 ofJens Kruse Andersen.

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

LINKS

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

Wikipedia,RSA-640

CROSSREFS

Cf.A108375.

Sequence in context:A136153 A069477 A325993*A206653 A202429 A236612

Adjacent sequences:A108570 A108571 A108572*A108574 A108575 A108576

KEYWORD

more,nonn

AUTHOR

Jason Earls,Jul 05 2005

EXTENSIONS

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

STATUS

approved