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 A136031 #21 Sep 06 2021 16:53:17
%S A136031 89,178481,2089,616318177,164511353,2099863,13264529,20394401,
%T A136031 3203431780337,761838257287,212885833,9361973132609,1113491139767,
%U A136031 57912614113275649087721,13842607235828485645766393,341117531003194129,3976656429941438590393
%N A136031 Largest prime factor of composite Mersenne numbers.
%H A136031 Amiram Eldar, <a href="/A136031/b136031.txt">Table of n, a(n) for n = 1..183</a>
%F A136031 a(n) >= A089158(n). - _R. J. Mathar_, May 01 2008
%t A136031 FactorInteger[2^#-1][[-1,1]]&/@Select[Prime[Range[40]],!PrimeQ[2^#-1]&] (* _Harvey P. Dale_, May 05 2012 *)
%t A136031 With[{c=Complement[Prime[Range[PrimePi[200]]],MersennePrimeExponent[ Range[ 15]]]},Table[ FactorInteger[ 2^p-1][[-1,1]],{p,c}]] (* _Harvey P. Dale_, Sep 06 2021 *)
%Y A136031 Cf. A049479, A016047, A003260, A136030.
%K A136031 nonn
%O A136031 1,1
%A A136031 _Artur Jasinski_, Dec 11 2007
%E A136031 Corrected by _Harvey P. Dale_, May 05 2012