This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A108573 #21 May 16 2025 14:32:54 %S A108573 3,390,1334,136,2058,2710,2082,748,2388,3588,1902,988,9170,5076,28778, %T A108573 2112,1800,3082,1238,12916,5090,22312,8412,11068,2,1558,67710,3018, %U A108573 22554,1212,3692,29940,204,31432,15392,2922,4524,11418,12638,5500,12158,4626,15384,5718 %N A108573 Least positive k such that k * [RSA-640]^n - 1 is prime, where RSA-640 is the 193 decimal digit RSA challenge number. %C A108573 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_. %C A108573 RSA-640 was factored in 2005; see the Wikipedia link. - _D. S. McNeil_, Nov 26 2010 %H A108573 Michael S. Branicky, <a href="/A108573/b108573.txt">Table of n, a(n) for n = 0..81</a> %H A108573 Wikipedia, <a href="http://en.wikipedia.org/wiki/RSA-640">RSA-640</a> %Y A108573 Cf. A108375. %K A108573 nonn %O A108573 0,1 %A A108573 _Jason Earls_, Jul 05 2005 %E A108573 Edited and a(19) added by _D. S. McNeil_, Nov 25 2010 %E A108573 a(0) prepended and a(20) and beyond from _Michael S. Branicky_, May 16 2025