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 A088284 #21 Mar 17 2023 12:54:27
%S A088284 919,929,99999199999,99999999299999999,9999999992999999999,
%T A088284 999999999999919999999999999,99999999999999499999999999999,
%U A088284 999999999999999999999949999999999999999999999,99999999999999999999999999899999999999999999999999999
%N A088284 Palindromic primes in which a single digit is sandwiched between nonempty strings of 9's.
%H A088284 Alois P. Heinz, <a href="/A088284/b088284.txt">Table of n, a(n) for n = 1..20</a>
%H A088284 Hans Havermann, <a href="http://gladhoboexpress.blogspot.ca/2016/03/near-rep-nine-palindromic-primes.html">Near-rep-nine palindromic primes</a>
%t A088284 Select[Flatten[Table[FromDigits[Join[PadRight[{},n,9],{d},PadRight[{},n,9]]],{n,30},{d,Range[8]}]],PrimeQ] (* _Harvey P. Dale_, Mar 17 2023 *)
%Y A088284 Subsequence of A002385.
%Y A088284 Cf. A088281, A088282, A088283.
%K A088284 base,nonn
%O A088284 1,1
%A A088284 _Amarnath Murthy_, Sep 29 2003
%E A088284 More terms from _David Wasserman_, Aug 03 2005
%E A088284 Name clarified by _Christian Stump_, Mar 31 2015