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 A358699 #41 Dec 01 2022 12:40:56 %S A358699 3,5,7,31,13,257,73,683,127,331,109,61681,5419,2796203,8191,3033169, %T A358699 1321,599479,122921,38737,22366891,8831418697,2931542417,22253377, %U A358699 268501,131071,28059810762433,279073,54410972897,77158673929,145295143558111,2879347902817,10052678938039 %N A358699 a(n) is the largest prime factor of 2^(prime(n) - 1) - 1. %H A358699 Amiram Eldar, <a href="/A358699/b358699.txt">Table of n, a(n) for n = 2..197</a> (terms 2..120 from Hugo Pfoertner) %F A358699 a(n) = A006530(A098102(n)). - _Michel Marcus_, Nov 28 2022 %F A358699 a(n) = A005420(A006093(n)). - _Amiram Eldar_, Dec 01 2022 %o A358699 (PARI) forprime (p=3, 140, my(f=factor(2^(p-1)-1)); print1(f[#f[,1],1],", ")) %o A358699 (Python) %o A358699 from sympy import primefactors, sieve %o A358699 def A358699(n): return primefactors(2**(sieve[n]-1)-1)[-1] # _Karl-Heinz Hofmann_, Nov 28 2022 %Y A358699 Cf. A005420, A006093, A006530, A061286, A071243, A086019, A098102. %Y A358699 Subsequence of A005420 and of A274906. %K A358699 nonn %O A358699 2,1 %A A358699 _Hugo Pfoertner_, Nov 27 2022