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 A308079 #21 Mar 31 2024 02:08:31 %S A308079 10974881,193949641,717653129,8762386393,19683169273,24802217129, %T A308079 78618861353,121271968201,146050578391,169905267617,188684740591, %U A308079 232153956569,290762221753,306091598201,336675266287,394233108121,592050558553 %N A308079 Pseudoprimes to base 3 that divide a Mersenne number. %C A308079 Members of A005935 that divide a member of A001348. %C A308079 Odd members k of A005935 such that the multiplicative order of 2 modulo k is a prime. Odd members k of A005935 such that A002326((k-1)/2) is prime. %C A308079 The known entries are proper divisors of a Mersenne number. It is not known if the Mersenne number itself can belong to this sequence. %H A308079 Amiram Eldar, <a href="/A308079/b308079.txt">Table of n, a(n) for n = 1..202</a> (terms below 10^15) %H A308079 Mersenne Forum, <a href="https://www.mersenneforum.org/showthread.php?p=516206#post516206">Composite PRP (discussion thread)</a>. %e A308079 10974881 is in the sequence because it divides 2^239 - 1 (and 239 is prime), it is not a prime, but 3^10974880 === 1 (mod 10974881). %o A308079 (PARI) forstep(n=3,+oo,2,Mod(3,n)^(n-1)==1&&!ispseudoprime(n)&&ispseudoprime(znorder(Mod(2,n)))&&print1(n,", ")) %Y A308079 Intersection of A005935 and A122094. %Y A308079 Subsequence of A052155. %Y A308079 Cf. A001348, A002326. %K A308079 nonn %O A308079 1,1 %A A308079 _Jeppe Stig Nielsen_, May 11 2019