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 A102249 #17 Jan 24 2020 12:55:50
%S A102249 10,13,31,36,51,57,61,69,72,78,79,90,91,97,117,120,127,129,135,138,
%T A102249 153,156,166,174,183,184,189,201,205,210,222,225,226,234,237,240,241,
%U A102249 244,252,261,265,273,276,280,285,292,304,306,309,318,322,325,327,337,345
%N A102249 Numbers k such that k1111 is prime.
%H A102249 Daniel Starodubtsev, <a href="/A102249/b102249.txt">Table of n, a(n) for n = 1..10000</a>
%e A102249 At k=10, k1111 = 101111 (prime).
%e A102249 At k=90, k1111 = 901111 (prime).
%e A102249 At k=138, k1111 = 1381111 (prime).
%t A102249 Select[ Range[ 350], PrimeQ[ FromDigits[ Flatten[ IntegerDigits /@ { #, 1, 1, 1, 1}]]] &] (* _Robert G. Wilson v_, Feb 21 2005 *)
%t A102249 Select[Range[400],PrimeQ[#*10^4+1111]&] (* _Harvey P. Dale_, Jul 14 2019 *)
%Y A102249 Cf. A024912.
%K A102249 nonn,base
%O A102249 1,1
%A A102249 _Parthasarathy Nambi_, Feb 18 2005
%E A102249 More terms from _Robert G. Wilson v_, Feb 21 2005