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 A263875 #12 Nov 22 2015 15:23:24 %S A263875 1,2,3,4,5,8,10,20,29,955,4583176,9092392 %N A263875 a(n) = least positive k such that A263874(n) + 2^k is prime. %C A263875 A263874 gives where the records occur. %H A263875 mersenneforum.org, <a href="http://www.mersenneforum.org/forumdisplay.php?f=86">Five or Bust - The Dual Sierpinski Problem</a> %o A263875 (PARI) a=1; forstep(n=1, 773, 2, k=1; while(!ispseudoprime(n+2^k), k++); if(k+1>a, print1(k, ", "); a=k+1)); %Y A263875 Cf. A067760, A263874. %K A263875 nonn,hard,more %O A263875 1,2 %A A263875 _Arkadiusz Wesolowski_, Oct 28 2015