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 A023585 #19 Sep 24 2023 03:56:02 %S A023585 3,5,3,13,3,5,3,37,3,3,61,73,3,5,3,3,3,11,7,3,5,157,3,3,193,3,5,3,7,3, %T A023585 11,3,3,277,3,7,313,5,3,3,3,19,3,5,3,397,421,5,3,457,3,3,13,3,3,3,3, %U A023585 541,7,3,5,3,613,3,5,3,661,673,3,17,3,3,733,5,757,3,3,13,3,19,3 %N A023585 Least prime divisor of 2*prime(n)-1. %H A023585 Harvey P. Dale, <a href="/A023585/b023585.txt">Table of n, a(n) for n = 1..1000</a> %t A023585 FactorInteger[#][[1,1]]&/@(2Prime[Range[90]]-1) (* _Harvey P. Dale_, Oct 08 2017 *) %o A023585 (PARI) a(n) = factor(2*prime(n)-1)[1, 1]; \\ _Michel Marcus_, Oct 01 2013 %Y A023585 Cf. A020639, A076274. %K A023585 nonn %O A023585 1,1 %A A023585 _Clark Kimberling_ %E A023585 Definition edited by _Michel Marcus_, Oct 01 2013