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 A230667 #5 Oct 28 2013 13:47:10 %S A230667 3,3,3,641,280743771536011781 %N A230667 Smallest starting number for n consecutive odd numbers that are primes or pseudoprime (base 2). %C A230667 It is conjectured that the sequence is full, that is, a(6) does not exist. %e A230667 First and smallest occurrence of n, n >= 1, consecutive odd numbers that are primes or pseudoprimes (base 2): %e A230667 a(1) = 3: (3) ; %e A230667 a(2) = 3: (3, 5) ; %e A230667 a(3) = 3: (3, 5, 7); %e A230667 a(4) = 641: (641, 643, 645, 647); (645 is pseudoprime base 2 and others are prime); %e A230667 a(5) = 280743771536011781: (280743771536011781, 280743771536011783, 280743771536011785, 280743771536011787, 280743771536011789); (280743771536011785 is pseudoprime base 2 and others are prime). %Y A230667 Cf. A001567, A228455. %K A230667 nonn,hard %O A230667 1,1 %A A230667 _Shyam Sunder Gupta_, Oct 27 2013