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 A218830 #18 Aug 04 2019 06:38:52
%S A218830 3449,1711,73,15,6227,1051,2239,2599,7723,781,1163,587,11443,2279,157,
%T A218830 587,32041,1051,2083,4681
%N A218830 Largest odd integer not of the form p+2q with p, q, p^2+4(2^n-1)q^2 all prime, or 0 if there would be no such upper bound.
%C A218830 This is the sequence M defined in a comment to A218825.
%C A218830 _Zhi-Wei Sun_ has conjectured (Nov 07 2012) that for any n>0, there is only a finite number of positive odd integers not of the given form. See arXiv:1211.1588.
%H A218830 Zhi-Wei Sun, <a href="http://arxiv.org/abs/1211.1588">Conjectures involving primes and quadratic forms</a>, arxiv:1211.1588 [math.NT], 2012-2017.
%e A218830 The exceptionally low values a(3), a(4) and a(15) correspond to the sets:
%e A218830 E(3) = {1,3,5,7,31,73} = { 2n-1: for no prime q, both p=2n-1-2q and p^2+28*q^2 are prime },
%e A218830 E(4) = {1,3,5,7,9,11,13,15} = { 2n-1: A218825(n)=0 },
%e A218830 E(15) = {1,3,5,7,9,13,15,31,33,35,37,73,89,157} = { 2n-1: for no prime q, both p=2n-1-2q and p^2+4(2^15-1)q^2 are prime }.
%Y A218830 Cf. A218825, A046927, A000040.
%K A218830 nonn,more
%O A218830 1,1
%A A218830 _Zhi-Wei Sun_ and _M. F. Hasler_, Nov 07 2012