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 A196023 #21 Apr 03 2023 10:36:12
%S A196023 16661,76667,3166613,3466643,7466647,7666667,145666541,148666841,
%T A196023 152666251,155666551,169666961,176666671,181666181,304666403,
%U A196023 305666503,307666703,308666803,329666923,347666743,349666943,373666373,374666473,383666383,391666193,397666793
%N A196023 Primes that are palindromes and have 666 in the middle.
%D A196023 _N. J. A. Sloane_, personal communication, 2011.
%H A196023 Arkadiusz Wesolowski, <a href="/A196023/b196023.txt">Table of n, a(n) for n = 1..1000</a>
%H A196023 G. L. Honaker, Jr. and Chris Caldwell, <a href="https://t5k.org/curios/cpage/21318.html">Prime Curios! 3166613</a>
%H A196023 Wikipedia, <a href="http://en.wikipedia.org/wiki/Number_of_the_Beast">Number of the Beast</a>
%H A196023 <a href="/index/Pac#palindromes">Index entries for sequences related to palindromes</a>
%t A196023 Select[Table[FromDigits@Join[Flatten@IntegerDigits@PadLeft[{666}, 2, n], Reverse@IntegerDigits[n]], {n, 397}], PrimeQ] (* _Arkadiusz Wesolowski_, Dec 03 2011 *)
%Y A196023 Subsequence of A131645.
%K A196023 base,nonn
%O A196023 1,1
%A A196023 _Arkadiusz Wesolowski_, Sep 26 2011