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 A256621 #31 Mar 14 2023 09:15:31
%S A256621 3893257,9023533,11005327,11659009,18747809,21855233,25183007,
%T A256621 34074379,54298687,58562951,60496981,89891273,94277683,96602887,
%U A256621 102276859,115555927,117578429,122191543,125115709,132837283,138169991,139442753,168852077,183879649,184904831
%N A256621 Primes p such that the decimal expansion of p remains prime under three iterations of base-10 to base-2 conversion.
%H A256621 Sebastian Petzelberger, <a href="/A256621/b256621.txt">Table of n, a(n) for n = 1..10000</a>
%H A256621 Carlos Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_280.htm">Puzzle 280. 3893257</a>, The Prime Puzzles and Problems Connection.
%e A256621 The 3 iterations: 3893257 --> 1110110110100000001001 --> ... --> ... are prime.
%o A256621 (PARI) isok(n, nb=3) = {for (k=1, nb, b = binary(n); d = eval(subst(Pol(b), x, 10)); if (! isprime(d), return (0)); n = d;); return (1);} \\ _Michel Marcus_, Apr 08 2015
%Y A256621 Cf. A065720, A123266, A256622.
%K A256621 nonn,base
%O A256621 1,1
%A A256621 _Sebastian Petzelberger_, Apr 06 2015