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 A228845 #15 Feb 16 2025 08:33:20 %S A228845 1,2,4,8,16,7,8,9,11,11,12,13,14 %N A228845 Least m such that (2k+1)*2^m + 1 is a prime factor of the Fermat number 2^(2^n) + 1. %C A228845 a(n) >= n + 2 for n >= 2. %C A228845 a(n) = A228846(n) if 2^(2^n) + 1 is prime or semiprime. %H A228845 Wilfrid Keller, <a href="http://www.prothsearch.com/fermat.html">Fermat factoring status</a> %H A228845 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FermatNumber.html">Fermat Number</a> %Y A228845 Cf. A000215, A019434, A023394, A046052, A228846. %K A228845 nonn,hard,more %O A228845 0,2 %A A228845 _Arkadiusz Wesolowski_, Sep 05 2013