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 A155508 #8 Aug 21 2020 13:23:16
%S A155508 199,91199,111119,111919,119191,991999,1191119,1191191,1191991,
%T A155508 11111911,11191991,11919991,19111991,91111199,111111199,111199199,
%U A155508 191111119,199991999,919919999,1111111999,1191111991,1199111191,1911199999
%N A155508 Lesser of emirps (pairs) with digits 1 and 9 only.
%H A155508 Harvey P. Dale, <a href="/A155508/b155508.txt">Table of n, a(n) for n = 1..660</a>
%t A155508 Flatten[Table[Select[Subsets[Select[FromDigits/@Tuples[{1,9},n],PrimeQ],{2}],AllTrue[#,PrimeQ]&&#[[1]]==IntegerReverse[#[[2]]]&][[All,1]],{n,3,10}]/.{}->Nothing] (* _Harvey P. Dale_, Aug 21 2020 *)
%Y A155508 A006567, A155507, A155509
%K A155508 nonn,base
%O A155508 1,1
%A A155508 _Lekraj Beedassy_, Jan 23 2009
%E A155508 More terms from _Sean A. Irvine_, Apr 06 2010