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 A056800 #13 Jun 12 2017 19:00:39
%S A056800 0,2,4,8,28,32,448,2108,3112,76264
%N A056800 Numbers n such that 6*9^n +1 is prime.
%C A056800 a(11) > 10^5. - _Robert Price_, Jun 04 2015
%t A056800 Do[If[PrimeQ[6*9^n + 1], Print[n]], {n, 0, 1000}]
%t A056800 Select[Range[3000], PrimeQ[6 9^# + 1] &] (* _Vincenzo Librandi_, Sep 28 2012 *)
%o A056800 (PARI) is(n)=ispseudoprime(6*9^n+1) \\ _Charles R Greathouse IV_, Jun 12 2017
%K A056800 nonn
%O A056800 1,2
%A A056800 _Robert G. Wilson v_, Aug 22 2000
%E A056800 a(8) from _Vincenzo Librandi_, Sep 28 2012
%E A056800 a(9)-a(10) from _Robert Price_, Jun 04 2015