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 A020307 #11 Aug 06 2015 12:55:30 %S A020307 91,121,511,671,703,949,1387,1541,1729,1891,2701,2821,3281,3367,3751, %T A020307 5551,6643,7381,8401,8695,8911,10585,11011,12403,12991,14383,15203, %U A020307 15251,15841,15863,16471,16531,18721,19345,23521,24661,24727,26335,28009,29341 %N A020307 Strong pseudoprimes to base 81. %H A020307 R. J. Mathar, <a href="/A020307/b020307.txt">Table of n, a(n) for n = 1..300</a> %H A020307 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a> %K A020307 nonn %O A020307 1,1 %A A020307 _David W. Wilson_