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 A096498 #13 Nov 13 2017 19:51:34
%S A096498 7,109,1109,11093,111109,1111091,11111101,111111109,1111111097,
%T A096498 11111111059,111111111103,1111111111093,11111111111053,
%U A096498 111111111111053,1111111111111039,11111111111111107,111111111111111091,1111111111111111037,11111111111111111027,111111111111111111053,1111111111111111111097
%N A096498 Prime before n-th repunit.
%H A096498 Robert Israel, <a href="/A096498/b096498.txt">Table of n, a(n) for n = 2..999</a>
%F A096498 a(n) = A002275(n) - A096870(n) = A096497(n) - A096499(n).
%p A096498 seq(prevprime((10^n-1)/9), n=2..50); # _Robert Israel_, Nov 13 2017
%t A096498 Table[NextPrime[(10^n - 1)/9, -1], {n, 2, 22}] (* updated by _Michael De Vlieger_, May 02 2016 *)
%o A096498 (PARI) a(n) = precprime((10^n-1)/9 - 1); \\ _Michel Marcus_, May 02 2016
%Y A096498 Cf. A068693, A002275, A096497.
%K A096498 nonn
%O A096498 2,1
%A A096498 _Labos Elemer_, Jul 09 2004