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 A280003 #30 Feb 16 2025 08:33:38 %S A280003 14,120,290,320,95330,2167800 %N A280003 Numbers k such that 7*2^k + 1 is a prime factor of a Fermat number 2^(2^m) + 1 for some m. %C A280003 18233956 belongs to this sequence, but its position is currently unknown. - _Jeppe Stig Nielsen_, Oct 05 2020 %H A280003 Proth Search Page, <a href="http://www.prothsearch.com/fermat.html">Prime factors of Fermat numbers</a> %H A280003 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FermatNumber.html">Fermat Number</a> %o A280003 (Magma) IsInteger := func<k | k eq Floor(k)>; [n: n in [1..320] | IsPrime(k) and IsInteger(Log(2, Modorder(2, k))) where k is 7*2^n+1]; %Y A280003 Subsequence of A032353. %Y A280003 Cf. A000215, A050527, A057778, A201364, A204620, A226366, A280004. %K A280003 nonn,hard,more %O A280003 1,1 %A A280003 _Arkadiusz Wesolowski_, Feb 21 2017