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 A020249 #13 Aug 11 2014 22:45:15 %S A020249 169,265,553,1271,2701,4033,4371,4681,6533,6541,7957,8321,8651,8911, %T A020249 9805,14981,18721,25201,31861,34133,44173,47611,47783,50737,57401, %U A020249 62849,82513,96049,109061,113737,140807,153181,163933,177193,182071,210493,210799 %N A020249 Strong pseudoprimes to base 23. %H A020249 R. J. Mathar, <a href="/A020249/b020249.txt">Table of n, a(n) for n = 1..686</a> %H A020249 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a> %K A020249 nonn %O A020249 1,1 %A A020249 _David W. Wilson_