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 A139099 #9 Sep 12 2019 12:29:16
%S A139099 1,3,5,9,11,13,19,25,29,37,53,59,61,67,83,101,107,121,131,139,149,163,
%T A139099 173,179,181,197,211,227,269,293,317,347,349,373,379,389,419,421,443,
%U A139099 461,467,491,509,523,541,547,557,563,587,613,619,653,659,661,677,701
%N A139099 Numbers 2n+1 for which A002326(n) are record values of A002326.
%C A139099 Question: does this sequence contain infinitely many composite numbers?
%C A139099 Nonprimes in the sequence are 1, 9, 25, 121, 1369,... (no more up to at least 100000). [_R. J. Mathar_, Jul 14 2010]
%H A139099 Amiram Eldar, <a href="/A139099/b139099.txt">Table of n, a(n) for n = 1..10000</a>
%t A139099 a[n_] := MultiplicativeOrder[2, 2 n + 1]; s = {}; am = 0; Do[a1 = a[n]; If[a1 > am, am = a1; AppendTo[s, 2 n + 1]], {n, 0, 360}]; s (* _Amiram Eldar_, Sep 12 2019 *)
%Y A139099 Cf. A002326, A001122.
%K A139099 nonn
%O A139099 1,2
%A A139099 _Vladimir Shevelev_, Jun 05 2008
%E A139099 More terms from _R. J. Mathar_, Jul 14 2010