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 A280004 #59 Feb 16 2025 08:33:38 %S A280004 67,9431,461081,2543551 %N A280004 Numbers k such that 9*2^k + 1 is a prime factor of a Fermat number 2^(2^m) + 1 for some m. %C A280004 Fernando (Remark 5.2) shows that all terms are odd. - _Jeppe Stig Nielsen_, Jan 02 2025 %H A280004 R. Fernando, <a href="https://ravif.web.illinois.edu/fermat_divisors.pdf">Morehead-like restrictions on Fermat divisors</a>. %H A280004 Proth Search Page, <a href="http://www.prothsearch.com/fermat.html">Prime factors of Fermat numbers</a> %H A280004 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FermatNumber.html">Fermat Number</a> %Y A280004 Subsequence of A002256. %Y A280004 Cf. A000215, A050528, A057778, A201364, A204620, A226366, A280003. %K A280004 nonn,hard,more %O A280004 1,1 %A A280004 _Arkadiusz Wesolowski_, Feb 21 2017