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 A135977 #11 May 23 2021 02:51:19
%S A135977 536870911,8796093022207,140737488355327,9007199254740991,
%T A135977 2361183241434822606847,9444732965739290427391,
%U A135977 604462909807314587353087
%N A135977 Mersenne composites (A065341) with exactly 3 prime factors.
%H A135977 Amiram Eldar, <a href="/A135977/b135977.txt">Table of n, a(n) for n = 1..42</a>
%F A135977 a(n) = 2^A344515(n) - 1. - _Amiram Eldar_, May 23 2021
%t A135977 k = {}; Do[If[ ! PrimeQ[2^Prime[n] - 1], c = FactorInteger[2^Prime[n] - 1]; d = Length[c]; If[d == 3, AppendTo[k, 2^Prime[n] - 1]]], {n, 1, 40}]; k
%Y A135977 Subsequence of A065341.
%Y A135977 Cf. A000225, A054723, A134852, A135975, A135976, A135978, A135979, A344515.
%K A135977 nonn
%O A135977 1,1
%A A135977 _Artur Jasinski_, Dec 09 2007