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 A020159 #17 Aug 03 2014 14:01:11
%S A020159 6,10,15,30,49,65,66,133,185,451,481,561,637,931,946,1105,1221,1729,
%T A020159 1813,2317,2405,2465,2553,3310,4753,4921,6241,6289,6601,7107,7421,
%U A020159 7449,8177,8911,9073,9131,10470,10585,10963,11041,12403,14191,16219,17767,18721
%N A020159 Pseudoprimes to base 31.
%C A020159 Composite numbers n such that 31^(n-1) == 1 (mod n).
%H A020159 R. J. Mathar and T. D. Noe, <a href="/A020159/b020159.txt">Table of n, a(n) for n = 1..1000</a> (R. J. Mathar 837 terms)
%H A020159 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>
%t A020159 base = 31; 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 A020159 Cf. A001567 (pseudoprimes to base 2).
%K A020159 nonn
%O A020159 1,1
%A A020159 _David W. Wilson_