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 A366171 #22 Dec 02 2024 06:52:28 %S A366171 3,7,19,27,31,39,151,199,451,2371,2511,7859,103819 %N A366171 Integers k such that (2^(k+3)-2^k-1)/5 is prime. %C A366171 If p = (2^(k+3)-2^k-1)/5 is prime, then 2^(k+2)*p is a strongly 2-near perfect number. %C A366171 a(14) > 2*10^5. - _Michael S. Branicky_, Dec 02 2024 %H A366171 Vedant Aryan, Dev Madhavani, Savan Parikh, Ingrid Slattery, and Joshua Zelinsky, <a href="https://arxiv.org/abs/2310.01305">On 2-Near Perfect Numbers</a>, arXiv:2310.01305 [math.NT], 2023. See p. 15. %o A366171 (PARI) isok(k) = my(x=(2^(k+3)-2^k-1)/5); (denominator(x)==1) && ispseudoprime(x); %Y A366171 Cf. A366172 (strongly 2-near perfect numbers). %K A366171 nonn,more %O A366171 1,1 %A A366171 _Michel Marcus_, Oct 03 2023 %E A366171 a(13) from _Michael S. Branicky_, Oct 05 2023