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 A020198 #22 Jun 12 2015 10:52:49
%S A020198 69,169,213,341,377,561,671,703,781,897,949,1441,1541,1633,1649,1891,
%T A020198 2001,2201,2701,2769,2873,3053,3201,4061,4331,4371,4899,4901,6001,
%U A020198 6177,6409,6681,7449,7991,9301,9361,11661,12121,12209,12337,12441,12673,12881
%N A020198 Pseudoprimes to base 70.
%C A020198 Composite numbers n such that 70^(n-1) == 1 (mod n). - _Michel Lagneau_, Feb 18 2012
%H A020198 T. D. Noe, <a href="/A020198/b020198.txt">Table of n, a(n) for n = 1..1000</a>
%H A020198 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>
%t A020198 base = 70; 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 *)
%t A020198 Select[Range[10^4], Not[PrimeQ[#]] && PowerMod[70, # - 1, #] == 1 &] (* _Alonso del Arte_, Jun 12 2015, based on _Farideh Firoozbakht_'s program for A005939 *)
%o A020198 (PARI) forcomposite(n=4,1e6, if(Mod(70,n)^(n-1)==1, print1(n", "))) \\ _Charles R Greathouse IV_, Jun 12 2015
%Y A020198 Cf. A001567 (pseudoprimes to base 2).
%K A020198 nonn
%O A020198 1,1
%A A020198 _David W. Wilson_