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 A145097 #14 Mar 12 2020 05:26:24
%S A145097 89,178481,2304167,616318177,164511353,20408568497,59862819377,
%T A145097 1416003655831,3203431780337,761838257287,10334355636337793,
%U A145097 21514198099633918969,224958284260258499201,57912614113275649087721
%N A145097 a(n) is the largest proper divisor of the Mersenne composite A065341(n).
%C A145097 Note that not all the largest divisors are primes.
%C A145097 Which divisors are prime? - see A145099. - _Artur Jasinski_, Oct 04 2008
%H A145097 Amiram Eldar, <a href="/A145097/b145097.txt">Table of n, a(n) for n = 1..183</a>
%t A145097 a = {}; Do[m = 2^Prime[n] - 1; If[PrimeQ[m], null, AppendTo[a, Divisors[m][[ -2]]]], {n, 1, 40}]; a
%Y A145097 Cf. A065341, A135975, A135980, A136031.
%K A145097 nonn
%O A145097 1,1
%A A145097 _Artur Jasinski_, Oct 01 2008
%E A145097 Name clarified by _Amiram Eldar_, Mar 12 2020