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 A263874 #11 Nov 22 2015 15:23:13 %S A263874 1,7,23,31,47,61,139,271,287,773,2131,40291 %N A263874 Integers for which the smallest k in A067760 such that n + 2^k is prime increases. %H A263874 mersenneforum.org, <a href="http://www.mersenneforum.org/forumdisplay.php?f=86">Five or Bust - The Dual Sierpinski Problem</a> %o A263874 (PARI) a=1; forstep(n=1, 773, 2, k=1; while(!ispseudoprime(n+2^k), k++); if(k+1>a, print1(n, ", "); a=k+1)); %Y A263874 Cf. A067760, A123252. %Y A263874 A263875 gives the record values. %K A263874 nonn,hard,more %O A263874 1,2 %A A263874 _Arkadiusz Wesolowski_, Oct 28 2015