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 A230668 #8 Dec 08 2016 20:44:57 %S A230668 280743771536011781,666787209284980781,1386744766793550161, %T A230668 6558237049521329741,11646802313400102461 %N A230668 Smallest of 5 consecutive odd numbers that are primes or pseudoprime (base 2). %C A230668 It is conjectured that all numbers in this sequence ends in 1. %C A230668 All terms known so far are of the form A228455(n) - 4. - _M. F. Hasler_, Dec 08 2016 %e A230668 280743771536011781 is in sequence because 280743771536011781, 280743771536011783, 280743771536011785, 280743771536011787, 280743771536011789 is a set of 5 consecutive odd number where 280743771536011785 is pseudoprime base 2 and others are prime. %Y A230668 Cf. A001567, A228455. %K A230668 nonn,hard,more %O A230668 1,1 %A A230668 _Shyam Sunder Gupta_, Oct 27 2013 %E A230668 Definition reworded by _M. F. Hasler_, Dec 08 2016