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 A066845 #16 Apr 19 2019 12:01:02
%S A066845 3,5,3,17,11,13,43,257,57,205,683,241,2731,3277,331,65537,43691,4033,
%T A066845 174763,61681,5419,838861,2796203,65281,1016801,13421773,261633,
%U A066845 15790321,178956971,80581,715827883,4294967297,1397419,3435973837
%N A066845 a(n) = (lcm_{k=0..n} (2^k + 1))/(lcm_{k=0..n-1} (2^k + 1)).
%C A066845 The primitive part of 2^n + 1. Bisection of A019320. - _T. D. Noe_, Jul 24 2008
%H A066845 T. D. Noe, <a href="/A066845/b066845.txt">Table of n, a(n) for n = 1..1000</a>
%F A066845 a(n) = cyclotomic(2*n, 2). - _Vladeta Jovovic_, Apr 05 2004
%t A066845 Cyclotomic[2*Range[40],2] (* _Harvey P. Dale_, Apr 19 2019 *)
%o A066845 (PARI) a(n) = polcyclo(2*n, 2); \\ _Michel Marcus_, Mar 06 2015
%Y A066845 Cf. A051844, A034268, A019320.
%Y A066845 Cf. A019320.
%K A066845 easy,nonn
%O A066845 1,1
%A A066845 _Vladeta Jovovic_, Jan 20 2002