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 A107290 #4 Apr 03 2023 10:36:10 %S A107290 3,11,43,2731,43691,174763,715827883,768614336404564651, %T A107290 206323339880896712483187371,54086425609737787797192670096043, %U A107290 56713727820156410577229101238628035243 %N A107290 Numbers (M_k+2)/3 where M_k is a Mersenne prime > 6. %C A107290 Many small values are prime; (M_89+2)/3 is the first composite. %H A107290 C. K. Caldwell, The Prime Glossary, <a href="https://t5k.org/glossary/page.php?sort=NewMersenneConjecture">Bateman, Selfridge, Wagstaff; the New Mersenne Prime Conjecture</a> %Y A107290 Cf. A000668. %K A107290 nonn %O A107290 3,1 %A A107290 _Yasutoshi Kohmoto_, May 22 2005 %E A107290 Edited by _Don Reble_, May 23 2005