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 A020151 #14 Aug 03 2014 14:01:10
%S A020151 22,33,91,154,165,169,265,341,385,451,481,553,561,638,946,1027,1045,
%T A020151 1065,1105,1183,1271,1729,1738,1749,2059,2321,2465,2501,2701,2821,
%U A020151 2926,3097,3445,4033,4081,4345,4371,4681,5005,5149,6253,6369,6533,6541,7189,7267
%N A020151 Pseudoprimes to base 23.
%C A020151 Composite numbers n such that 23^(n-1) == 1 (mod n).
%H A020151 R. J. Mathar, <a href="/A020151/b020151.txt">Table of n, a(n) for n=1..1085</a>
%H A020151 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>
%t A020151 base = 23; t = {}; n = 1; While[Length[t] < 100, n++; If[! PrimeQ[n] && PowerMod[base, n-1, n] == 1, AppendTo[t, n]]]; t (* _T. D. Noe_, Feb 21 2012 *)
%Y A020151 Cf. A001567 (pseudoprimes to base 2).
%K A020151 nonn
%O A020151 1,1
%A A020151 _David W. Wilson_